I/O subsystem using slow devices

ABSTRACT

An I/O subsystem uses a peripheral-controller for handling data transfer operations between a host computer and a plurality of peripheral terminals. The peripheral controller is made of (a) a universal processor, which generates instructions for executing data transfer operations, and (b) an application dependent logic module which particularly adapts the instructions to each peripheral terminal connected to the system. Upon recognition of the use of addresses for slow memories, slow registers or &#34;slow devices&#34;, control logic in the application dependent logic module controls the clocking in the universal processor to slow data transfer rates for data being placed in or removed from the &#34;slow devices&#34;.

This is a continuation-in-part of parent case U.S. Ser. No. 308,721, filed Oct. 5, 1981, and now abandoned. The parent case U.S. Ser. No. 308,721 was a continuation-in-part of the grandparent case U.S. Ser. No. 052,821, filed June 27, 1979, and previously abandoned.

BACKGROUND

1. Field of the Invention

This invention relates to peripheral controllers used in I/O systems for controlling data transfer operations between a main host computer and a plurality of peripheral terminal units.

This application is a continuation-in-part of U.S. Ser. No. 052,821, filed June 27, 1979 now abandoned, and entitled "Microprocessor System Operating With Normal or Slow Memories", inventors Brian K. Forbes and Robert D. Catiller.

2. Cross References to Related Applications

This application is related to the following patent applications filed as follows:

A patent application entitled "Microprocessor System Facilitating Repetition of Instructions", inventors Robert D. Catiller and Brian K. Forbes, filed June 27, 1979, U.S. Ser. No. 052,687 and now U.S. Pat. No. 4,292,667.

A patent application entitled "Microprocessor System with Source Address Selection", inventors Robert D. Catiller and Brian K. Forbes, filed June 27, 1979, U.S. Ser. No. 052,477 and now U.S. Pat. No. 4,290,106.

A patent application entitled "Microprocessor Having Word and Byte Handling", inventors Robert D. Catiller and Brian K. Forbes, filed June 27, 1979, U.S. Ser. No. 052,478 and now U.S. Pat. No. 4,301,505.

A patent application entitled "Digital System for Data Transfer Using Universal Input-Output Microprocessor", inventors Robert D. Catiller and Brian K. Forbes, filed June 27, 1979, U.S. Ser. No. 052,336 now U.S. Pat. No. 4,293,909.

A patent application entitled "Microprocessor System with Specialized Instruction Format", inventors Brian K, Forbes and Robert D. Catiller, filed June 27, 1979, U.S. Ser. No. 052,350 now U.S. Pat. No. 4,291,372.

Certain prior patents of the assignee of this invention form a background and understanding of the type of I/O systems used herein and these patents, listed below, are included herein by reference.

U.S. Pat. No. 4,162,520 to Darwen J. Cook and Donald Millers II entitled "Intelligent Input/Output Interface Control Unit for Input-Output Subsystem". This patent described a unit called a Data Link Processor for handling I/O data transfers.

U.S. Pat. No. 4,189,769 to Darwen J. Cook and Donald Millers II entitled "Input-Output Subsystem for Digital Data Processing System". This patent described peripheral-controllers organized into base module units to form an I/O subsystem.

U.S. Pat. No. 4,280,193 to Kenneth W. Baun and Jimmy G. Saunders entitled "Data Link Processor for Magnetic Tape Data Transfer System". This patent described a peripheral-controller made of a standardized card, called Common Front End, and a particularized card called the PDB or Peripheral-Dependent Board.

Prior Art

Microprocessors and microprocessor systems will be seen to generally follow the architectural formulas and interrelationships which were established from general computer technology. However, microprocessors making use of large scale integrated techniques can be made into small packages with the use of integrated circuit chips and will generally follow the pattern of using a central processing unit, memory input-output circuits and various other control and support circuitry.

It is typical that the architecture of microprocessors will generally use a program counter which is used to select some portion of memory to be addressed for retrieving program instruction codes to be executed.

In the usage of a system where a central or main host processor operates in conjunction with a number of remotely located "base modules" which base modules support a group of peripheral-controllers which service and control external peripheral units, a considerable amount of circuitry has been required to provide data transfer capability on an efficient basis and also to cater to the specific needs of each type of peripheral unit.

Heretofore each peripheral-controller which was situated in a base module was burdened with many processor and control circuits for handling the specific requirements of each peripheral terminal unit leading to a heavy burden of circuitry in each peripheral-controller.

SUMMARY OF THE INVENTION

To alleviate the burden of costly circuitry for each peripheral controller, a universal or architecturally standard microprocessor was developed which would provide a multiplicity of processing functions for use in a peripheral-controller so that the peripheral-controller would only need a limited amount of application dependent logic and circuitry for handling the particular types of peripherals which it serviced. Thus, the universal processor, or as it is called here, the "universal I/O state machine", could serve as a standard unit for all types of peripheral-controllers so that each of the peripheral-controllers would only need to have the minimum amount of circuitry and programs required for application to the particular peripherals in the network.

Thus, with the use of the universal I/O state machine as a general purpose microprocessor in these applications, it became possible to reduce the cost, the quantity of circuitry, the space requirements and the system of architectural arrangements so that a more economical and more efficient architectural system could be established. Thus, with the advent of the described universal I/O state machine, there has been devised a generalized type of microprocessor which can serve as part of any type of peripheral-controller in a base module thus to handle any variety of peripheral terminal units. This generalized and simplified type of microprocessor (oriented to (a) addressing instructions and data and (b) manipulating data) executes its operations very rapidly and is designed to handle individual bytes for operations with peripheral devices which are "byte" oriented and also can execute processing and transfer operations with complete words (a word here being two 8-bit bytes symbolized as AB) for use with peripheral terminals which are "word oriented" and which can accept or transmit full words.

The universal microprocessor working in conjunction with the peripheral-oriented application dependent logic module permits the development of a generalized type of peripheral-controller which can handle a plurality of peripheral units instead of requiring a separate controller for each peripheral unit. Since the hardware and programming of the microprocessor remains standard and constant for each of the peripheral-controllers while the application dependent module is programmed to cater to a group of selected peripherals, it is thus possible to accomplish not only great versatility in data transfer and control features but also to provide great economies in circuitry and cost.

In digital systems where many instructions and control signals are required for the transfer of data to a variety of different types of peripheral units, generally a specifically tailored and designed peripheral-controller was provided which is particularly suited to handle the data transfers to and from a single particular type of peripheral unit. It was found that by providing a uniform microprocessor for all types of peripheral-controllers which only varied in the type of application dependent logic programs required for specific types of peripheral devices, that great economies of space and cost could be realized. Thus, the combination of a universal microprocessor working in conjunction with an application dependent module could form a peripheral-controller to serve data transfer functions previously requiring a series of peripheral controllers.

The processor of the peripheral-controller of the present invention, upon receipt of an I/O data transfer command from a host computer, will generate instructions and execute data transfer operations to/from peripheral terminals by use of an application dependent logic module which provides an external memory with instructions for peripheral terminal control and which has control logic which recognizes when slow devices are addressed. The control logic can then initiate a WAIT signal to said universal processor to slow down and regulate the rate of data transfers to slow memory and slow peripheral terminals.

A linear microsequencer circuit operates a decoder-controller in the microprocessor. The microsequencer includes a micro-instruction PROM which is sequentially stepped by a State Counter after being initiated by the "Clear" signal. The micro-instruction PROM also receives signals from an instruction register and flag registers. The micro-instruction PROM then provides Control Term signals for operation of the microprocessor system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall block diagram illustrating the use of a main host system computer with a plurality of base modules which support peripheral-controllers which communicate with peripheral devices.

FIG. 2 is a diagram of the peripheral-controller showing the elements of the universal input-output microprocessor state machine and its communication lines to the application dependent logic module. FIG. 2 is subdivided into two portions designated as FIG. 2A and FIG. 2B such that by juxtaposing FIG. 2A to the left of FIG. 2B (and FIG. 2B to the right of FIG. 2A) the continuity of connections between the two drawings may be seen. FIG. 2C is a schematic drawing of the decoder-controller with its linear sequencer circuitry; FIG. 2C-1 shows the state counts; FIG. 2D illustrates the addressing of selected accumulator registers and their relation to the arithmetic logic unit and I/O bus; FIG. 2E shows how source and destination addresses are accessed in one clock period; FIG. 2F is a schematic drawing illustrating the relationship between the repetition counter and repeat-mode flip-flop.

FIG. 3 is a schematic diagram showing certain memory addressing features of the UIO-State Machine, particularly the use of a dedicated bit designated as the "byte-swap" bit.

FIG. 4A is a perspective drawing of the input-output base module and showing major elements such as the distribution control card, the peripheral controller (line control processor) card and certain connections from the front plane (fore plane) to the host computer and to peripheral units. FIG. 4B is a schematic drawing showing circuit connections to the four front plane connectors. FIG. 4B is oriented such that it shows the first front plane connector while FIG. 4B-1 shows the second front plane connector. Orientation-wise the FIG. 4B-1 can be juxtaposed underneath the FIG. 4B in order to provide continuity to the connections shown between the two front plane connectors. FIG. 4B-2 illustrates connections to the front plane connector No. 3 and FIG. 4B-3 illustrates the connections to the front plane connector No. 4.

FIG. 5 is a timing diagram showing the clocking of output control registers of the UIO-state machine.

FIG. 6 is a circuit drawing showing how the program memory is enabled.

FIG. 7 is a timing diagram for the clear line.

FIG. 8 is a timing diagram showing the WAIT line timing.

FIG. 9 is a timing diagram showing timing for non-repeated GET/PUT functions.

FIG. 10 shows the timing diagrams for the repeated GET/PUT functions.

FIG. 11 is a diagram showing the correlated timing features for reading data from external memory on the memory data bus.

FIG. 12 is a timing diagram showing the timing correlations between the clock, the memory address signal and the memory write data on the I/O bus.

FIG. 13 is a timing diagram showing the relationship of the halt repetition function signal to the clock.

FIG. 14 is a timing diagram showing the relationship of the parity error signal to the clock and memory address signal.

FIG. 15A is a schematic drawing showing the transfer of data from the host computer to a slow memory device;

FIG. 15B is a schematic drawing showing the path whereby data is transferred from a slow memory device through the subsystem processor for processing and editing and thence return back to the slow memory device;

FIG. 15C shows the data transfer path from a slow memory device to the subsystem processor and back through an external register to a peripheral device;

FIG. 15D shows the data path for data transfer from a slow memory device over to an external register for subsequent transfer to a peripheral device.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is seen a system block diagram of a typical Burroughs host computer system, with central processing unit cabinet 100 having basically a series of main memory modules 101, a memory control module 102, a data processor module 103, working in cooperation with a host dependent port module 104. The host dependent port module provides a series of communication cables 105 designated as MLI or message level interfaces. These message level interfaces provide communication lines to a base module cabinet 106 (or a plurality of such cabinets) which are designated as the Universal Input/Output Base Module Cabinet. The base module cabinet is built to support a plurality of universal input/output (UIO) base modules 107. Each of these UIO base modules provides communication, control, and data transfer lines to specific types of peripheral devices.

It should be noted that the host dependent port module can have message level interfaces to a plurality of UIO base module cabinets. And likewise, each UIO base module cabinet may have message level interface communication lines to other host systems 200 (main memory and processor) in addition to the first described host system of FIG. 1.

In the preferred embodiment of the system to be described herein, it will be seen that a base module cabinet can support from one to four UIO base modules. Formerly each of the UIO base modules contained up to eight peripheral-controllers 108 known as "line control processors" and each of the line control processors were dedicated to data transfer and control with a particular type of peripheral device 109. This plurality of separate peripheral-controllers for each different peripheral has now been replaced with a single universal microprocessor and application dependent logic module which constitutes a single peripheral-controller for handling a plurality of peripheral terminals.

Another provision of the system will allow for a unit designated as a line expansion module (LEM) which can be inserted in the UIO base module so that a single message level interface can be extended to communicate with up to eight UIO base modules.

The host system as represented by the central processing unit cabinet 100 can communicate with up to 64 peripheral controllers (line control processors) for each message level interface (MLI), if the base module is provided with the unit known as an LEM or line expansion module.

As seen in FIG. 1, the host system 100 can have eight message level interfaces (MLI) and can thus communicate with up to 512 peripheral controllers (line control processors).

The peripheral controllers or line control processors (LCP) are controllers which are dedicated to data transfer and control between a peripheral terminal and the main host system or a plurality of host systems.

The peripheral controllers known as line control processors have been described, both in their system interrelationships and in their internal workings, in a number of previously filed patent applications and issued patents. These include the following United States Patents: U.S. Pat. No. 4,174,352 entitled "Modular Block Unit for I/O Subsystem", inventors Darwen J. Cook and Donald A. Millers, II; U.S. Pat. No. 4,106,092 entitled "Interface System Providing Interfaces to Central Processing Units and Modular Processor-Controllers for an Input-Output Subsystem", inventor Donald A. Millers, II; U.S. Pat. No. 4,162,520 entitled "Intelligent Input-Output Interface Control Unit for Input-Output Subsystem", inventors Darwen J. Cook and Donald A. Millers, II; and U.S. Pat. No. 4,189,769, entitled "I/O Subsystem for Digital Data Processing System", inventors Darwen J. Cook and Donald A. Millers, II, and these patents are included herein by reference.

The peripheral controllers known as line control processors (LCP's) may generally fall into types of categories. There is the 2-card LCP and the 3-card LCP.

The 2-Card LCP

This peripheral controller has a first card which is designated as the CFE or common front-end on which there are supplied a plurality of read-only memories (ROM's); hardware-wise these common front-end cards are of the same construction and nature except that in individual cases the ROMs are made to hold different programs which are suitable to the application at hand or the peripheral device with which it is used; thus, hardware-wise all the front-end cards will be found to be the same physically but only differ in the fact that different program material is inserted in the individual ROMs. The second card in the 2-card LCP is the PDC or peripheral dependent card. This card is uniquely built and adapted to suit the particular type of peripheral unit to which it communicates. It may be designated as an "application dependent logic module".

The 3-Card LCP

Here, again, the first card is the CFE or common front-end card which is physically the same except for different programming inside the ROM, this program being varied according to the application required. The second card is the CDC or common data card which is tailored to suit the requirements of different peripheral units; however, it may be the same for such a group of items as magnetic tape, punched card-tape, disk pack, and console controls. The third card of the 3-card LCP is designated as the PDC or peripheral dependent card. This card is unique and is designed to handle one particular type of peripheral device.

In FIG. 4A there is seen a more detailed perspective drawing of a typical I/O base module 107. A plurality of these base modules are housed and serviced by a base module cabinet 126 of FIG. 1.

The base module 107 provides housing whereby printed circuit cards holding integrated circuitry may be inserted on sliding tracks in order to connect with the backplane connectors for automatic connection into the system. A peripheral controller (or line control processor) 108 may require, as previously described, two printed circuit or three printed circuit cards. The base module may support up to eight such peripheral controllers in its housing. Communications between the base module and the host system are controlled by distribution card 110. Other specialized handling printed circuit cards may be inserted, such as the previously mentioned line expansion module, common front-end card, common data card; or a second distribution control card, etc., can be inserted for connection into said base module 107.

The frontplane or foreplane permits jumper cable connections 111 (FIG. 4A) between printed circuit cards and also permits connection cables such as message level interface 105 to the host computer or ribbon cable 109_(c) to permit connection from the base module to external devices such as peripheral device 109.

An interface panel 106 may be provided on the base module cabinet 120 to provide for cable connectors such as 104_(cc), 109_(cc) to facilitate disassembly and reconnection.

As was described in the previously mentioned patent references regarding line control processors, each base module unit is provided with a Distribution Control Card 110, FIG. 4A, which connects the message level interface from the main host system to a selectively addressed line control processor (peripheral controller) in that base module. Further, the base module has a common maintenance card and a common termination card which acts in common to service the entire group of up to eight line control processors in a base module.

The UIO base module may also support a line expansion module or LEM. This feature expands the usage of a UIO base module by adding another Distribution Control Card which permits connection of that base module to yet another main host system in addition to the one already connected to the first Distribution Control Card. Thus, communication from a main host system can be expanded to cover two or more UIO base modules and their attendant line control processors. Likewise, two or more host systems can be made to communicate to a UIO base module or a plurality of such base modules.

When it is desired to have one UIO base module connected to two main host computers, then a control card is used which is called the BCC or base control card. The base control card serves two basic functions; (a) to provide an interlock when multiple host computers try to access a base module, so that line control processors can thus be locked out from use by unauthorized host computers, and (b) to provide assorted features such as a base identification (ID) number and for maintenance control. The BCC is not mandatory when multiple hosts are connected to a base; however, it is useful. The base control card, however, can also be used when only a single host computer is connected to the UIO base module. Thus, the BCC is an independent and optional module, as is the line expansion module LEM.

Thus, in reference to FIG. 1, it should be stated that when a host computer is connected to a UIO base module, the base module must have at least one distribution card 110, FIG. 4A, for each host computer which is connected to it. Now, when a UIO base module is connected to a multiple number of host computers, then there is need for the base module to be provided with a unit known as the PSM or path selection module. The path selection module is the control unit which regulates the communication to and from the multiple number of distribution cards in the UIO base module.

In the development of line control processors, such as indicated in the prior cited patents and references, it was found that the amount of logic required for adaptability to any given type of peripheral unit or to a variety of peripheral units required that expensive and space consuming logic circuitry be developed which would take large quantities of hardware and space requirements on printed circuit cards such that sometimes four or five extra logic cards were needed in order to complete a particular line control processor. Soon the cost and space requirements of these developments became prohibitive and better means were required for handling the variety of functions required of a line control processor.

In this situation a microprocessor-controller was developed which could handle all the basic logic for any variety of peripheral terminal units and which could be built with a minimum amount of components and placed on a single printed circuit card. This device was designated as the universal input/output state machine or UIO-SM. Thus, the UIO state machine could be built typically on a 112 chip circuit board and be placed within the slide-in card rack which is supported by the LCP base module (now called UIO base module). The UIO state machine can interface easily to any application dependent logic through its front plane and, except for power connections and clock connections, no connections needed to be made to the LCP or UIO base backplane. The universal I/O state machine is basically implemented in transistor type logic (TTL).

General Overview of the Universal I/O State Machine

The UIO-SM has been made to implement a useful group of general purpose operators which include:

Arithmetic OP's

Logical OP's

Read/Write Memory OP's

PUT/GET OP's

Program Stack OP's (Branch, Call and Return)

In FIG. 2, there is shown a schematic diagram of a peripheral-controller for the I/O Subsystem of the present invention. The peripheral-controller is composed of a UIO State Machine 1 and an associated Application Dependent Logic Module 60_(L) which provides an external memory 90, control logic 66 and external registers 60 which connect to host system 10 and to peripheral 109 (via adapter 109_(c)).

Referring to FIG. 2, the UIO State Machine 1 is seen to be provided with Instruction-Execution Logic 2, Memory Address Logic 3, Data Manipulation Logic 4, and an internal program memory 50.

In FIG. 2 the Application Dependent Logic Module 60_(L) is connected by busses 10, 11, 12, 16 to the State Machine 1. The Logic Module 60_(L) provides an external memory 90 plus bus logic 66' and interface control logic 66 which includes an address decoder 66_(ad) for sensing addresses of "slow" elements, and an external register 60 which has bus connections to the Host System 10 and Peripheral Terminals such as 109.

At FIGS. 2A and 2B there is seen an overall block diagram of the UIO state machine. The input/output lines at the bottom of the drawing are all front plane lines which connect to the peripheral's application dependent control (PDC) logic since it is desired that the UIO state machine itself be independent of any application type logic or of the special requirements of particular peripheral units.

Referring to the state machine block diagram of FIGS. 2A and 2B there will be seen a series of interconnecting lines 16, 17₁, 17₂, 18, 10, 19, 11, 12 and 20, which connect to the application dependent logic 60_(L). These lines are labeled, such as the external memory data output bus 12, the I/O and memory write parity line 18, the memory address bus 16, the memory write enable 19 (and other functions listed on FIG. 2), the direct memory access (DMA) request line 11 (and other functions on FIG. 2), in addition to the main I/O bus 10. Line 15 is the instruction output bus from the program PROM 50.

A program counter 41, having input lines from stack memory 45 and I/O bus 10, via 10_(f), provides an output line which feeds an input signal to the program PROM 50 (internal memory 50). A memory reference register 40 (MRR) receives its input signals via I/O bus 10 from accumulator registers 30, memory operand 31, and the save-MRR 47 (memory reference register-save). Repetition counter 42 also receives an input line via I/O bus 10 for signals from accumulator registers 30 and memory operand 31.

The stack memory 45, controlled by stack pointer 46, provides an output line to the program counter 41. The repetition counter 42 provides an output which feeds back around line 10_(f) over to the I/O bus 10 and also around to the accumulator registers 30.

Attached and receiving input from the I/O bus 10 is a control register 1 designated as item 37, a control register 2 designated as item 38 and a parity register 39. The control registers 37, 38 provide buffering of signals to application control register lines 17₁, 17₂. The parity generator 39 has an output line 18 (part of I/O bus 10) and provides "I/O and memory write" parity.

The memory output data bus 12 from RAM external memory 90 connects to the memory operand register 31 whose outputs feed to ALU 32 and parity check circuitry 21 which has an output line 20 to provide memory read parity to external memory 90. Data bus 12 also provides an input to the instruction register 22 which has an output line connecting to the input of the instruction decoder-controller 23. Situated within instruction decoder-controller 23 are external flag registers 23_(e), interrupt mask 23_(i), and state counter 23_(s).

Accumulator registers 30 actually comprise two seats of eight registers, one set designated 30_(f) (foreground accumulator registers) and the other set as 30_(b) (background). Each of the 16 registers are addressed and selected by an address line 23_(a) from the instruction decoder-controller 23.

The I/O bus 10 provides a channel to the accumulator registers 30 which have an output to the B input of the arithmetic logic unit 32. Another input A to the arithmetic logic unit 32 comes from the memory operand register 31 which gets its input from external memory via the memory output bus 12, or from internal memory via bus 15.

The arithmetic logic unit 32 (ALU) has one set of outputs which feed to the "foreground" flag register 35 and another set of outputs to the "background" flag register 36. These flag registers 35 and 36 form an output which is fed to the instruction decoder-controller 23. They are used to signal "foreground mode" conditions for normal operation and "background mode" conditions for interrupts or emergency operation.

The F output of the arithmetic logic unit 32 feeds on a bus 10_(i) to the shift logic circuitry 33 and to the byte-swap circuitry 34. The outputs of these circuits 33, 34 connect to the I/O bus 10.

Summary: General Operation

The PUT OP (operator) writes a 16-bit word (two bytes symbolized as AB) from the I/O bus 10 into a selected application dependent register 60 (external register), the particular register being addressed via GET-PUT address lines 19. The PUT OP can address any one of 32 application dependent registers. The GET OP reads a 16-bit word from a selected application dependent register 60 into an accumulator register 30 on the UIO-SM or into RAM memory 90 through the I/O bus 10. The GET OP can also address a selected one of the 32 application dependent registers 60 (external registers).

The UIO-SM has the ability to repeat certain OP's (PUT's, GET's and logical OP's) by loading a number N (from the software) into a repetition counter 42 to control the memory reference register (MRR) 40 which is used as a counter after having been loaded with the starting address of the data block to be used in the "repeated" OP. A more detailed discussion of this operation is presented hereinafter in connection with FIG. 2F.

In order to hold "PUT Data" for a longer period of time than can occur directly off of I/O bus 10, there are two 8-bit registers (control registers 37, 38) which have been placed in the UIO-SM. The strobing of these registers 37, 38 is under the control of the application dependent logic 60_(L) (FIG. 2).

A "WAIT line" (on bus 11) has been built into the UIO-SM such that when an external "slow memory" is addressed, the "slow memory" can force the UIO-SM to wait however long required for the Read or the Write to be valid. This is seen on FIG. 2 at bus 11 which feeds signals to the instruction decoder-controller 23. This line can also be used to halt the machine. A clock enable line on bus 11 (CLKENB) has been included so that the application dependent logic 60_(L) may control the state machine clock for single pulse operations and also direct memory access (DMA) operations. The timing for this signal is the same as the WAIT signal on bus 11.

As seen in the state machine diagram of FIG. 2, the UIO-SM can check via ciruitry 21 for odd parity on each memory fetch. All memory fetches from external memory 90 come on the memory output data bus which is shown as bus 12 and which connects to instruction register 22 and to the memory operand register 31. All memory writes go out on the I/O bus 10 along with odd parity on line 18. The UIO-SM contains 8-K words of user-defined instruction programs in PROM 50 which is capable of being expanded to 64-K words.

With reference to FIG. 3, it will be seen that memory addresses can come from two sources--the program counter 41 and the memory reference register (MRR) 40. The UIO-SM provides the ability to do condition and unconditional Branches, Calls and Returns. "Calls" can be nested up to 16 levels from stack memory 45. The memory reference register 40 stores addresses and is used (at certain times specified in instruction words) to address RAM data memory 90 which will provide programs applicable to the peripheral device connecting to the application dependent logic module 60_(L). This external memory 90 also serves to store data which is being transferred between the host computer and the peripheral terminal device. Since memory 90 and 50 are organized two bytes wide (16-bits plus parity) but the data for transfer is sometimes required in single byte form, as for peripherals such as card readers, the memory reference register (MRR) 40 has been designed such that only the high order 15-bits are used to address memory 90. The low order bit (BYTESWP) is used by the byte-oriented read/write OP's to determine whether or not to byte-swap the two byte data word before storage into accumulator registers 30 on an "external data memory read" or before storage into external RAM data memory 90 on a "data memory write". This particular feature permits the UIO-SM to easily handle byte-oriented data in that the desired byte is automatically read into the "low order" byte position of the accumulator registers 30 on "data memory reads", as well as being automatically written from the "low order" byte position into the correct byte position on "data memory writes". The "high order" byte position of the accumulator registers 30 must contain the last byte written, if any is present.

In Table I there is shown the instruction format for the UIO-state machine operators. The external memory output data bus 12, or internal memory instruction bus 15, provides 17 bits designated 0-16. The bus bits 0-7 (low order) constitute the "B" byte while the bus bits 8-15 constitute the "A" byte (high order).

                                      TABLE I                                      __________________________________________________________________________     INSTRUCTION FORMAT FOR UIO-STATE                                               MACHINE OPERATORS                                                                                       Bus Bit on                                                                     Instruction Bus                                                           Field                                                                               15 and Memory                                         Field               Specifier                                                                           Data Bus 12                                           __________________________________________________________________________     Odd Parity          P    16                                                    Basic Function      F1   15                                                                        F0   14                                                    Function Variant    V4   13                                                                        V3   12                                                                        V2   11                                                                        V1   10                                                                        V0   9                                                     Destination Specifier                                                                              D3   8                                                     (or Misc. Control)  D2   7                                                                         D1   6                                                                         D0   5                                                     Source Accumulator  S2   4                                                                         S1   3                                                                         S0   2                                                     Memory Address Source                                                                              M    1                                                     For Operand of                                                                 Instruction                                                                    Copy ALU Output to  C    0                                                     Memory Reference Register                                                      Bus Bit 15-8 = "A" Byte                                                        Bus Bit 7-0 = "B" Byte                                                          ##STR1##                                                                      __________________________________________________________________________

As will be seen from Table I certain fields are specified such as the P field for odd parity, the basic function field F1, F0, and function variant field by V4-V0. The destination specifier field is designated D3-D0; the source accumulator field is designated S2, S1, S0. The field which causes selection of the memory address source to be used in fetching the operand of the instruction is designated M; while the function field for copying the arithmetic logic unit output into the memory reference register 40 is designated by the field C.

The odd parity bit is set such that an odd number of 1's will exist across the entire 17-bit instruction (or the operand). The basic function field F1, F0 is described in Table II such that various binary digit combinations of F1, F0 provide certain functions as shown.

                  TABLE II                                                         ______________________________________                                         BASIC FUNCTION                                                                 F1    F0    Function                                                           ______________________________________                                         0     0     Contents of External Register to Accumulator                                   or External RAM Memory (GET)                                       0     1     Contents of Accumulator or External RAM                                        Memory to External Register (PUT)                                  1     0     ALU Operators                                                      1     1     Program Stack Operators (Branch, Call, Return)                     ______________________________________                                    

For example, the GET function provides for the transfer of the contents of an external register 60 has the accumulator 30 or to RAM memory 90. The digital bits 0, 1 provide for the transfer of the contents of an addressed register in accumulator 30 (or an addressed portion of external RAM memory 90) to the external registers 60. This is called the PUT function. The F field bits 1, 0 provide for execution of the arithmetic logic unit operators; while bits 1, 1 provide for the functions of the program stack (45) operators such as Branch, Call, Return.

Table III shows the function variant field V4-V0 and its relation to the function field F1, F0.

                  TABLE III                                                        ______________________________________                                         FUNCTION VARIANT                                                               F1  F0    V4 V3 V2 V1 V0                                                                               Field Description                                      ______________________________________                                         0   0     [ R(N) ]      External Register Address (GET)                        0   1     [ R(N) ]      External Register Address (PUT)                        1   0     [ ALU OP ]    ALU Op Code                                            1   1     [ (OP) (TEST) ]                                                                              Program Stack Op Code and                                                      Condition Test Specifier                                                       (Conditions from Flag Register)                                                (ICall & IRet are                                                              Unconditional Operators)                                             OP = 00 IRet                                                                   OP = 01 Call                                                                   OP = 10 Branch                                                                 OP = 11 Return or ICall                                                        Test = 000                                                                             Unconditional                                                          Test = 001                                                                             ALU = 0                                                                Test = 010                                                                             ALU MSB = 0                                                            Test = 011                                                                             ALU Carry = 1                                                          Test = 100                                                                             ALU LSB = 0                                                            Test = 101                                                                             External Flag 1 = 1                                                    Test = 110                                                                             External Flag 2 = 1                                                    Test = 111                                                                             External Flag 3 = 1                                      ______________________________________                                          Note:                                                                          The Program Stack OP's can Execute on Condition Test True or Not True          depending on the Destination Specifier. IRet and ICall execute                 Unconditionally.                                                         

For example, the F-bits 0, 0 specify a GET operation from an external register while the F-bits 0, 1 specify a PUT operation into an external register of a specified address.

Table IV shows the destination specifier field, D3, D2, D1, D0.

                  TABLE IV                                                         ______________________________________                                         DESTINATION SPECIFIER (OR MISC. CONTROL)                                       D3  D2    D1    D0  Destination (Or Misc. Control)                             (i) GET and ALU OP's                                                           0   0     0     1   Null, No Destination - Used to Update Flag                                     Register only (ALU Op's Only)                              0   X     X     0   Write RAM Memory (GET and ALU Op's)                        1   [ A(D) ]  Destination Accumulator A(D) (GET and ALU                                      Op's) can be same as Source                                                    Accumulator A(S)                                                 (ii) PUT and Program Stack Op's                                                S   X     F     F   S = 0  Operand Source from Memory (PUT                                                and Program Stack Op's)                                                 S = 1  Operand Source from Source                                                     Accumulator A(S) (PUT and                                                      Program Stack Op's)                                                     FF = 00                                                                               Application Dependent Strobe No. 1                                             (PUT Op)                                                                FF = 01                                                                               Application Dependent Strobe No. 2                                             (PUT Op) Execute on Condition Test                                             True (Program Stack Op)                                                 FF = 10                                                                               Application Dependent Strobe No. 3                                             (PUT Op) Execute on Condition Test                                             Not True (Program Stack Op)                                             FF = 11                                                                               Load Repetition Count Register                                                 (Repeat Register 42) (PUT Op)                       ______________________________________                                          X = Don't care                                                           

This D3-D0 field is subdivided into (i) GET and ALU OP's and (ii) PUT and program stack OP's. In the case of (i) there may be no destination specified; or only a miscellaneous control field may be used to update the flag register; or the destination may be the RAM memory 90.

In the case (ii) for the destination field, the operand source may come from RAM memory 90; or the operand source may be from the source accumulator 30; or the destination may be a load into the repetition counter 42.

The Source Accumulator Field S2, S1, S0 is shown in Table V below:

                  TABLE V                                                          ______________________________________                                         SOURCE ACCUMULATOR A(S) FIELD                                                  S2, S1, S0                                                                     ______________________________________                                         (i) ALU or PUT                                                                 [ A(S) ] Operand from Source Accumulator A(S)                                           [can be same as Destination Accumulator A(D)]                         (ii) GET                                                                       S = XX0  Application Register 60 is Source                                     S = XX1  Repetition Counter 42 is Source                                       (iii) Program Stack OP's                                                       V = 11CCC & S = XX0                                                                             Return Operator                                               V = 11XXX & S = XX1                                                                             ICall Operator (Forced by                                                      Interrupt Hardware)                                           ______________________________________                                    

The source accumulator field specified as S2, S1, S0 (Table V) may apply (i) to the ALU or the PUT Op where the operand from the source accumulator A(S) can be the same as the destination accumulator A(D); or (ii) where the GET Op can function so that the source is an external application register 60 or that the source is the repetition counter 42; or wherein (iii) the program stack Op's can provide a return operator or an ICall operator.

M Field Specifier: Selecting Memory Address Source for the Operand of an Instruction

The M field specifier (as originally noted in Table I) may occur as one of two binary states, that is as a 0 or as a 1. When M is 0, then the operand for this instruction is located one address beyond this instruction (PC+1, program counter plus 1) or there is no operand. If the instruction does not require a memory operand, then PC+1 is not used for an operand; the next "instruction" will be at PC+1 (no space is allowed for an operand). The operators that do not use an operand are listed as follows:

1. All "GET" operators;

2. "PUT" operators with D3=1;

3. "CALL" or "BRANCH" with D3=1;

4. ICALL, RETURN, IRETURN, ROTR, SHFL, SHFR, CMA, ONES, ZERO, SWAC, WRTW, WRTB, DRTL, EI, DI and RSTK Operators. (These operators are discussed subsequently hereinafter).

When the M field bit is "1", then the operand for this instruction is addressed by the memory reference register 40 (MRR) or else there is no memory operand for this instruction.

C Field: For Copying ALU Output to the Memory Reference Register 40

The C field originally shown in Table I may read as a 1 bit or a 0 bit. In the 1 bit situation this means that the machine will not copy the ALU output to the memory reference register 40; however, if the bit is "0", then the ALU output will be copied on to the memory reference register 40. The C bit can be set to 0 on all instructions except GET's and RDB, RDBW, RBWR, SWAC and WRTB. These operators are discussed subsequently hereinafter.

Flag Registers

Two flag registers are provided so that at least one flat register is fully available for each of the two operating modes. Thus, flag register 35 is the "foreground mode" flag used under normal operating conditions while register 36 is the "background mode" flag which is used during interrupt or other unusual conditions. As seen in FIG. 2, flag registers 35, 36 receive output from the arithmetic logic unit 32 and provide an output line to feed input to the instruction decoder-controller 23. The flag register is updated at the end of all ALU operators (which include arithmetic OP's, logical OP's and load/store/move OP's). On OP's which "byte swap" the ALU 32 output before storage into the destination location, the flag register is updated on the basis of the full two bytes of information from the ALU 32 after being swapped. In the specific cases of REBW OP (read before write byte) and the RBWR OP (read before write byte reversed), a full memory word is read into the UIO state machine, but only one of the two bytes read is written into accumulator register 30 (the low order byte of the accumulator destination register remains unchanged). The flag registers (35,36) are updated on the basis of the full word read from RAM memory 90.

As indicated in FIG. 2, the accumulator registers 30 actually constitute two different sets of eight registers. One set 30_(f) of accumulator registers is for normal operating conditions (foreground mode) while the other set 30_(b) of eight accumulator registers is for abnormal conditions (background mode) as during interrupts.

Instruction Repetition

The use of the repetition counter 42 provides an instruction repetition feature where a PUT or a GET OP may be repeated up to 256 times by the use of a PUT OP to load the repetition counter 42 which must be followed by the PUT or the GET OP to be repeated. Any value N from 0 to 255 (from the software) may be loaded into the repetition counter 42 and N+1 operations will be performed (1 to 256). The address source for the repeated PUT data or the address destination for the repeated GET data is found in MRR 40 and thus these addresses will originate from the memory reference register 40 and not from the program counter 41 (PC+1). In other words, the M-bit is set to "1" in the repeated PUT or GET. After each PUT or GET OPs, the hardware will increment the MRR 40 in preparation for the next PUT or GET. When repeated, each individual PUT or GET will execute in one clock period, unless the PUT or the GET addresses a "slow memory", in which case there will be one extra clock period at the beginning of the repeated PUT's or at the end of the repeated GET's.

The use of the repeated PUT's or GET's serves to greatly increase code compaction while also greatly increasing the speed of the clock transfers to or from RAM memory 90.

Any logical OP (AND, CMA, CMM, OR, XOR, ONES, ZERO, ADDC, SUBC, etc. as described hereinafter) may be repeated up to 256 times by the use of a PUT OP to load the repetition counter 42 which must be followed by the logical OP to be repeated. Any value of N from 0 to 255 may be loaded into the repetition counter 42 and N+1 operations will be performed (1 to 256). For the repeated OP to work as expected, the source accumulator 30 should be equal to the destination accumulator 30. The address source for the operand data should originate from the memory reference register 40 (MRR) just as for the repeated PUT or GET. After each OP of the repeat sequence is executed, the hardware will increment MRR 40 in preparation for the next OP. When repeated, each individual logical OP will execute in one clock period, unless the operands are located in a "slow memory".

One particular case, where a repeated logical OP can increase code compaction and execution speed, is the use of the repeated "Exclusive OR" for the purpose of generating longitudinal parity on a data block located in external memory 90.

The PUT OP which loads the repetition counter 42 must have the N value in the "B" byte (low order 8-bits) of the PUT data. The "A" byte (high order 8-bits) is a "don't care".

The application dependent logic 60_(L) has the capability of stopping instruction repetition even though the full number of operations has not occured, as will be later discussed in connection with FIG. 2F.

The capability exists to do repeat operations with PC (program counter 41) used for the memory operand source address (M-bit equal to 0). In this case, PC 41 will increment during the repeat operation instead of MRR 40 (provided that the operator does use a memory operand). Using PC 41 during the repeated operations will allow the use of a multiple word literal following the single repeated operator. The size of the "literal" field must be exactly the number of words specified by the repeat count values plus 1 word. The HLT REP/interface line (halt repetition) must remain "high" during all repeat operations using PC 41 as an address source for operand data.

In regard to the instruction execution speed, the basic clock rate for the UIO-SM is 8 MHZ (125 nanosecond clock period). All OP's, with the exception of the program stack operators, execute in two clock periods except such OP's that write from the UIO-SM accumulators 30 into RAM memory 90 (3 clocks required) or have operands to be fetched from or stored into "slow memory" (three or more clocks required). The program stack operators require 3 clock periods to execute if the condition is true (Branch or Call "executed") and only require 2 clock periods if the condition is false (Branch or Call "not executed"). The NO-OP executes in 2 clock periods. The OP IReturn executes in 3 clock periods, while Load and Store Accumulator executes in 4 clock periods.

The execution of any given instruction requires an "instruction fetch" along with the above-noted execution cycles; however, in the case of the UIO-SM, the instruction fetch for the next instruction is performed during the last execute cycle of the current instruction. Therefore, the "instruction fetch" is masked from the timing.

The NO-OP

The NO-OP consists of any program stack operator (such as Branch) with the condition test field set to "UNCONDITIONAL" and the destination specifier set to "EXECUTE ON CONDITION TEST NOT TRUE" (Branch never). Whether or not the NO-OP occupies one or occupies two memory locations, is a function of whether or not the operand (Branch never address) is located next to the instruction (PC+1) or is addressed by the memory reference register 40 or comes from an accumulator 30. The flag registers 35, 36 will not be updated on the NO-OP.

Clear Sequence

The clear sequence is a "zeroing" operation. When a "Clear" is issued to the UIO-SM, the program counter 41, the repetition counter 42, and the stack pointer 46 are reset to zero and an instruction is fetched. After a "Power-up Clear" has been issued, the accumulators 30 cannot be predicted. However, if a "Clear" is issued while power remains up, the accumulator registers 30 will retain their states just previous to the "Clear". While "Clear" is true, at least two clocks must be issued; after "Clear" has gone false, one clock is required before execution of the first instruction begins.

Output Control Registers

There are two output control registers 37 and 38 in the UIO-SM as seen in FIG. 2. These can be used by the application dependent logic 60_(L) to hold "PUT Data" for a longer period of time than can normally occur directly off of the I/O bus 10. Both output control registers 37 and 38 are 8-bits wide and have their data inputs connected to the low order 8 bits of the I/O bus 10 ("B" byte). Both of these output control registers must be clocked by the application dependent logic 60_(L). FIG. 5 illustrates a preferred method for clocking the output control registers 37 and 38. A triple input NAND gate 74 in FIG. 5 has three input line signals: PUT STROBE/signal; address signals for an external register (60 of FIG. 2); and the clock signal. These signals are correlated in FIG. 5.

Once clocked by a leading edge, the outputs of these registers will stabilize in 17 nanoseconds or less. A Schottky TTL NAND device 74 is used for the control register clock generator since the "PUT Data" can be guaranteed for only 10 nanoseconds past the leading edge of CLOCK as received on the UIO-SM, and the output control registers require a data hold time of 2 nanoseconds minimum past the leading edge of their clock.

Memory Addressing and Expansion

In the preferred embodiment and without expansion of memory, the UIO-SM has the capability of directly addressing 0 to 64K words of program memory 50, FIG. 2, and from 0 to 32K words of data memory in RAM 90. To facilitate any further expansion of memory, such as by using paging techniques or otherwise, the enabling of the program PROM 50 in the UIO-SM can be controlled by an expanded memory in the application dependent logic 60_(L).

FIG. 6 illustrates how such an expanded memory can control the enabling of the UIO-SM program PROM 50 through the use of a front-plane external signal. If the expanded memory drives this signal to a "high" level, the UIO-SM program PROM 50 will be disabled. If the application dependent logic 60_(L) does not have a requirement for expanded memory, then it will simply tie this line to a logic "low". In FIG. 6, a 5-input NOR gate 75 has inputs from program counter 41 in order to provide a parity disable signal (high) to disable PROM 50.

The UIO-SM program PROM 50 may be expanded from 8K up to 64K words by using different size PROMs. The chip select and the addressing functions of the PROM 50 are automatically adjusted without circuit changes. A jumper arrangement is used to enable the parity bit output for the size of the program memory being used. With reference to FIG. 6, jumpers can be installed according to the following Table VI for each word size of PROM shown below.

                  TABLE VI                                                         ______________________________________                                          8K PROM          A15 to MADR 15                                                                 A14 to MADR 14                                                                 A13 to MADR 13                                               16K PROM          A15 to MADR 15                                                                 A14 to MADR 14                                                                 A13 to GND                                                   32K PROM          A15 to MADR 15                                                                 A14 to GND                                                                     A13 to GND                                                   64K PROM          A15 to GND                                                                     A14 to GND                                                                     A13 to GND                                                   ______________________________________                                    

The UIO-SM receives its clock signal from the backplane of the UIO base module. To receive clock signals, the UIO-SM preferably uses Schottky type flip-flops followed by Schottky type inverters in order to generate the internal UIO-SM clock (CLOCK). All the timings are relative to this internal clock which preferably has a minimum delay of four nanoseconds and a maximum delay of 13 nanoseconds from the clock on the backplane. In order to insure minimum clock skew between the application logic 60_(L) and the UIO-SM, the application logic 60_(L) is preferably made to use the same type of devices to receive and distribute the clock.

The following paragraphs will illustrate detailed timing and explanation for the interface between the UIO-SM and the application dependent logic 60_(L).

Referring to FIG. 7, which is entitled "Clear Line Timing", it will be seen that in order to initialize the UIO-SM, the CLEAR line must be "true" (active low) for at least two full clock periods.

Another feature implemented into the UIO-SM is the WAIT line (WAIT/). This is used such that when "slow memory" is addressed, the slow memory can force the UIO-SM to wait however long required for the "read" or the "write" to be valid. This line can also be used to halt the machine for any length of time required. The timing requirements for the WAIT/line are illustrated in FIG. 8. Since this line has multiple sources, including one line on the UIO-SM itself, it must be driven by an open-collector (TTL device).

Referring to FIG. 8, the state machine processor has a clock signal derived from the backplane of the base module. This clock, when not disabled, will execute data transfers from the I/O bus to external devices at the clock rate. But this rate would be too rapid for "slow" external devices to accept the high speed rate of the microprocessor.

The application dependent logic module 60_(L) (FIGS. 2A-2B) has Control Logic 66 (with an internal Address Decoder, FIG. 2) which recognizes any addresses directed to the external memory/external register means. These types of addresses originate from the memory reference register 40 or the instruction register 22. Upon recognition of addresses directed to external devices (external memory/external register means) the Control Logic 66 will initiate the WAIT signal to the microprocessor system which will "disable" the clock for one or more clock cycles. Thus, data to be transferred from the I/O bus will be held until the clock signal resumes. Depending on the "slowness" of the external devices, the WAIT signal can be programmed or set to disable 1, 2, . . . x clock cycles, thus to delay data transfer from the I/O bus 10 to the external devices.

In addition, if the external devices are busy (not ready) the Control Logic 66 is connected to sense this, and can further maintain the WAIT signal longer until the external device is "ready" (not busy).

When the WAIT signal is shut off by the Control Logic 66, then the clock signal in the microprocessor system resumes, and data transfers again are effectuated.

A CLOCK enable (CLOCKENB) line is implemented on the UIO-SM for use in single pulse or for direct memory access (DMA) functions. The timing here is the same as the WAIT/of FIG. 8.

GET/PUT Timings

The timing relationships for the non-repeated GET's and PUT's are illustrated in FIG. 9. The WAIT line can be used on the GET to increase the memory write time in the case of a "slow" write memory. Another application for use of the WAIT line on GET's is to increase the amount of time available for the application dependent logic 60_(L) to drive the "GET DATA" and meet set-up times after having received the GET enable signal.

In the case of the PUT OP, the effect of the WAIT line is to increase the period of time that "PUT DATA" is on the I/O bus 10, although the UIO-SM would be halted during this time. It should also be noted that the timing of the PUT Strobe can only be guaranteed relative to the CLOCK signal and not relative to the PUT DATA. As such, neither edge of the PUT Strobe is used to directly clock the PUT Data into an application dependent register 60.

The first transfer of data in a "repeated" GET to an addressed register in accumulator 30 will be invalid. All data transfers (after the first) will be valid. The same accumulator register 30 is addressed as a "destination" for each repeat GET operation.

If M=1 (refer to Table I), the memory reference register 40 will be incremented during each repeat GET operation, even though external RAM memory 90 is not used by the GET operator.

The timing relationships for repeated GET's and repeated PUT's are shown in FIG. 10. Specifically this timing chart further illustrates when repeated "GET Data" can change and when repeated "PUT Data" will also change.

The timing relationships for memory "Reads" in the UIO-SM are shown in FIG. 11. The WAIT line has been utilized on one of the memory reads to illustrate how one (or more) extra clock periods can be inserted after address stabilization to allow "slow access" memory to meet the setup time requirements of the UIO-SM.

In regard to the memory "Write" timings for the UIO-SM, these memory Writes are shown in FIG. 12. UIO-SM instructions which can do memory Writes are: WRTW (Write Word), WRTB (Write Byte), and also GET. The WAIT line 11 has been utilized on one of the memory Writes to illustrate how one (or more) extra clock periods can be inserted after address stabilization in order to allow "slow" Write memory an adequate Write time.

Halting "Repeated" Instructions

Although the total number of operations on a repeated instruction may not be completed, the repeated instruction itself can be halted by the application dependent logic 60_(L). The application dependent logic produces the signal HLTREP/(active low), which is the signal to the UIO-SM that halts the repetition. In FIG. 13 there is shown the timing of this signal. If the application dependent logic 60_(L) has no requirement for halting repeated instructions, then the application dependent logic can simply leave the HLTREP/signal unconnected.

When the HLTREP signal goes false, the current processing operation will be completed and a fetch of the next instruction is started at the "high" clock transition. The HLTREP/line must remain "high" during repeat operations using the program counter (PC) 41 to address the memory operands (M bit=0).

Parity Error Line

On every memory fetch the UIO-SM checks for odd parity and signals the results to the application dependent logic 60_(L). If incorrect parity is detected, the UIO-SM takes no action other than to signal the error to the application dependent logic 60_(L). This timing of the parity error line PARERR/is shown in FIG. 14.

Referring to FIG. 3 and to the memory reference register 40 (MRR) there is a line which is used by external memory mapping logic to control address bit 15 of the memory reference register 40. This line is designated as MRR 15 and the state of this line is loaded into MRR 40 at bit 15 whenever a loading of memory reference register 40 is called for by a UIO-SM instruction. The state of this line should be stable for at least 30 nanoseconds prior to the high transition of the clock to ensure that it can be properly loaded. This line is tied to ground (low side) if memory mapping is not used.

There is a line designated IRQ/on bus 11 which line is the "interrupt request line". This line is driven "low" preferably by an open-collector device in order to request an interrupt of the UIO-SM. The UIO-SM will only recognize an interrupt request if the interrupt mask is reset (EI instruction executed, Table XII-F, for resetting the interrupt mask bit) and an instruction fetch has just been completed when not in repeat mode (high clock transition at end of TO and the start of T1).

The UIO-SM responds to an interrupt by forcing execution of an ICALL instruction and switching the UIO-SM "background" mode "on". The ICALL instruction generates an acknowledge signal (ACKI/) in order to allow the application logic 60_(L) to place an interrupt call address on the I/O bus 10. The ICALL instruction saves the memory reference register 40 data in the MRR save register 47 and it saves the old PC (program counter) value on the stack before loading PC with the call address (placed on the I/O bus 10 by the application logic 60_(L)). Further interrupts are inhibited in the "background" mode and the duplicate set of flaps (35) and accumulators (30_(f)) are used so that the "foreground" operating environment is preserved therein.

A return to the "foreground" mode is accomplished by executing an IRET instruction. The top value from the stack memory 45 is placed in the program counter PC 41 for the return address and the contents of the MRR save register 47 is placed into the memory reference register MRR 40. The original foreground flag 35 and foreground accumulator 30_(f) are again made active and contain the same values as before the interrupt. The clear line will place the UIO-SM in the "foreground" made and set the interrupt mask to disable interrupts. The IRQ/line must be stable at least 60 nanoseconds before the leading edge (high transition) of the clock signal.

The DMA request line 11 of FIG. 3 is a line which is driven "low" by the application dependent logic 60_(L) in order to isolate the UIO-SM address outputs on memory address bus line 16 so that direct memory access (DMA) logic can drive this bus. This line is left unconnected when not using the DMA.

The bus enable line (BUSEN/LINE) from Control Logic 66 is driven "low" by the application logic 60_(L) in order to enable the I/O bus drivers on I/O bus 10, including data, GETENB, PUTSTB and REGADR signals. The GETENB is a signal used to indicate that GET data is driven on to the I/O bus 10; the PUTSTB is the signal used to indicate that PUT data is on the I/O bus 10; the REGADR signal is the signal used to indicate the enabling of the external register address lines for GET's and PUT's. When "high", this line disables all I/O signals. This line is tied to "low" if it is not used.

Universal Input/Output State Machine Front Plane Interface

The front plane connectors (FIG. 4A, FIGS. 4B-1, 4B-2) which provide the interface for the UIO-SM are preferably four in number wherein each of the four front plane connectors provides 25 pin connections on each of two sides of each front plane connector. The following Tables VII-X show the signal name for each pin number for each side of the four front plane connectors.

                  TABLE VII                                                        ______________________________________                                         (Connector No 1) (See FIG. 4B-1)                                               PIN        $ SIDE*        # SIDE*                                              Number     SIGNAL NAME    SIGNAL NAME                                          ______________________________________                                         00         MADDR15        MADDR14                                              01         MADDR13        MADDR12                                              02         MADDR11        MADDR10                                              03         MADDR09        MADDR08                                              04         MADDR07        GND                                                  05         MADDR06        MADDR05                                              06         MADDR04        MADDR03                                              07         MADDR02        MADDR01                                              08         MADDR00        MRR15                                                09         BUSREQ/        GETSTB                                               10         IRQ/           PROMENB/                                             11         IOBUS15        IOBUS14                                              12         IOBUS13        IOBUS12                                              13         IOBUS11        IOBUS10                                              14         IOBUS09        IOBUS08                                              15         IOBUS07        IOBUS06                                              16         IOBUS05        IOBUS04                                              17         IOBUS03        IOBUS02                                              18         IOBUS01        IOBUS00                                              19         IOBUSP AR      REGADDR4                                             20         REGADDR3       GND                                                  21         REGADDR2       REGADDR1                                             22         REGADDR0       FLAG3/                                               23         FLAG2/         FLAG1/                                               24         HALTREP/       ACKI/                                                ______________________________________                                          *Note:                                                                         One side of connector is designated $ while the other side is desingnated      #.                                                                       

                  TABLE VIII                                                       ______________________________________                                         (Connector No. 2) (See FIG. 4B-1)                                              PIN        $ SIDE         # SIDE                                               NUMBER     SIGNAL NAME    SIGNAL NAME                                          ______________________________________                                         25         MEMOUT15       MEMOUT14                                             26         MEMOUT13       MEMOUT12                                             27         MEMOUT11       MEMOUT10                                             28         MEMOUT09       MEMOUT08                                             29         MEMOUT07       GND                                                  30         MEMOUT06       MEMOUT05                                             31         MEMOUT04       MEMOUT03                                             32         MEMOUT02       MEMOUT01                                             33         MEMOUT00       MEMOUTPA                                             34         OCREG107       OCREG106                                             35         OCREG105       OCREG104                                             36         OCREG103       OCREG102                                             37         OCREG101       OCREG100                                             38         OCREG207       OCREG206                                             39         OCREG205       OCREG204                                             40         OCREG203       OCREG202                                             41         OCREG201       OCREG200                                             42         OCREG1CK       OCREG2CK                                             43         RAMRD/         PUTSTB3/                                             44         PUTSTB2/       PUTSTB1/                                             45         CLKEN          GND                                                  46         unused         WAIT/                                                47         unused         CLEAR/                                               48         RAMWE/         unused                                               49         GETENB/        PARERR/                                              ______________________________________                                    

                  TABLE IX                                                         ______________________________________                                         (Connector No. 3) (See FIG. 4B-2)                                              PIN        $ SIDE         # SIDE                                               NUMBER     SIGNAL NAME    SIGNAL NAME                                          ______________________________________                                         50         BUSEN/                                                              51         BUSEN/                                                              52         IFETCH/                                                             53         IFETCH/                                                             54         BKG/FRG                                                             55         BKG/FRG                                                             ______________________________________                                          Note:                                                                          FIGS. 4B1 and 4B2 show in more detail the connectors 1, 2, 3, 4 of FIG.        4A.                                                                      

In addition to the microprocessor system elements shown in FIG. 2, FIG. 4B-1 indicates the connections to the PROM output registers 50_(r) and sub-elements of the instruction decoder-controller such as the repeat-mode flip-flop 42_(r) and foreground-background flip-flop 35_(f). FIG. 4B-2 shows further connections to the microprocessor system and includes a condition test register 23_(t).

                  TABLE X                                                          ______________________________________                                         (Connector No. 4) (See FIG. 4B-2)                                              PIN        $ SIDE         # SIDE                                               NUMBER     SIGNAL NAME    SIGNAL NAME                                          ______________________________________                                         75         MROEB/         MNTENB/                                              76         SC1B           SC2B                                                 77         SC1B           SC8                                                  78         STKOVF/                                                             79         SMOE/          GND                                                  80         BSAEOX/        BSBOEX/                                              81         SHAOEX         SHBOEX                                               82         MRSVOEX        RCOEX                                                83                        IIOAOEX/                                             84         FCLD/          MRLD/                                                85         MOPND/         REPEATB                                              86         INVOP          COND/                                                87         ACWRITE/       ACBWE/                                               88         SMWEX/         STKA0                                                89         STKA1          STKA2                                                90         STKA3          ENREP/                                               91         BYTSWP B       SCSOX                                                92         SCSIX          ALUMDX                                               93         ALUS3X         ALUS2X/                                              94         ALUS1X         ALUS0X                                               95         D3B            GND                                                  96         F0B            F1B                                                  97         ACADR0         ACADR1                                               98         ACADR2         SOB                                                  99         S1             S2                                                   ______________________________________                                    

Table XI is a glossary of the front plane signal names for the Universal I/O State Machine. This glossary shows the signal name, the number of the front plane connector involved, when the signal is a Fan-in or a Fan-out signal and, in addition, a functional description of the signal involved.

                                      TABLE XI                                     __________________________________________________________________________     GLOSSARY OF UIOSM FRONTPLANE SIGNAL NAMES                                      SIGNAL        CONNECTOR                                                                              FAN-IN/                                                  NAME          NUMBER  FAN-OUT*                                                                               DESCRIPTION                                      __________________________________________________________________________     1. MADDR15-   1       FD 75/40                                                                               Memory Address Bus                                  MADDR00                                                                     2. IRQ/       1       FI 1.25/3.16                                                                           Line that is used to                                                   (includes                                                                              interrupt the UIOSM.                                                   1100 ohm                                                                       pull-up res)                                             3. PROMENB/   1       FI 2.25/1.5                                                                            Expanded memory in                                                             the application                                                                dependent logic can                                                            drive this line which                                                          when high will allow                                                           the enabling of the                                                            program PROM on the                                                            UIOSM.                                           4. IOBUS15-   1       FO 373/38.75                                                                           BUS lines for GET data                              IOBUS00            FI 2.5/1.5                                                                             to UIOSM (or RAM) or                                                           PUT data to application                                                        dependent logic.                                 5. IOBUSPAR   1       FO 25/12.5                                                                             Odd parity line for                                                            IOBUS15-IOBUS00.                                 6. REGADDR4-  1       FO 75/40                                                                               External resister                                   REGADDR0                   address lines for                                                              GET's and PUT's                                  7. BUSREQ/    1       FI 5.75/9.65                                                                           When this line is held                                                         low the UIOSM address                                                          outputs are tri-stated.                                                        When this line returns                                                         high the Program                                                               Generator will be                                                              output on the address                                                          bus.                                             8. FLAG3/-    1       FI 1.25/3.16                                                                           Condition test lines                                FLAG1                      used by program stack                                                          operators.                                       9. HALTREP/   1       FI 1.25/4.25                                                                           Line which will stop                                                           a repeated instruction                           10.                                                                               MRR15      1       FI 1.25/0.25                                                                           Line that is used by                                                           mapping logic to                                                               control bit 15 of the                                                          memory reference                                                               register (MRR15).                                                              This line should be                                                            tied low if mapping                                                            is not used.                                        MEMOUT15-  2       FI 1.25/.25                                                                            Memory output bus.                                  MEMOUT00                                                                       MEMOUTPA   2       FI 1.25/.25                                                                            Memory output bus                                                              odd parity line.                                    OCREG107-  2       FO 160/12.5                                                                            Output control register                             OCREG100                   output data lines.                                  OCREG207-                                                                      OCREG200                                                                       OCREG1CK   2       FI 1.25/0.25                                                                           Clock line for output                               OCREG2CK                   control registers.                                  ACKI/      1       FO 75/40                                                                               Line that acknowledges                                                         that an interrupt                                                              request is being                                                               accepted by the UIOSM.                                                         When this signal is                                                            low, the application                                                           logic should place                                                             an interrupt call                                                              address on the I/O bus.                             PUTSTB3/-  2       FO 75/40                                                                               Lines that indicate                                 PUTSTB1/                   PUT data is on the                                                             I/O bus.                                            RAMRD/     2       FO 23.25/11.25                                                                         This line goes high                                                            at least 30 ns before                                                          RAMWE/ goes low. It                                                            may be used by appli-                                                          cation logic for                                                               generating a                                                                   synchronized version                                                           of RAMWE/.                                          WAIT/      2       FI 1.25/4                                                                              Line which causes                                                      (includes                                                                              the UIOSM to wait                                                      1100 ohm                                                                               one or more clock                                                      pull-up res)                                                                           periods.                                            CLR/       2       FI 1.25/3.16                                                                           Line which causes                                                      (includes                                                                              the UIOSM to                                                           1100 ohm pull-                                                                         clear.                                                                 up res)                                                  20.                                                                               RAMWE/     2       FO 25/12.5                                                                             Write enable for                                                               RAM.                                                GETENB/    2       FO 23/11.25                                                                            Line which indicates                                                           that GET data should                                                           drive into the I/O                                                             bus.                                                PARERR/    2       FO 25/12.5                                                                             Line that indicates                                                            a parity error was                                                             detected on the                                                                previous memory fetch.                              CLKEN      2       FI 1.25/4                                                                              Line that enables                                                      (includes                                                                              the UIOSM clock                                                        1100 ohm                                                                               when high.                                                             pull-up res)                                                GETSTB     1       FO 25/12.5                                                                             Line used with                                                                 GETENB/ for                                                                    application timing.                                 BUSEN/A    3       FI 5/5  When these lines go                                 BUSEN/B                    high, the I/O bus                                                              is disabled.                                        IFETCH/A   3       FO 75/40                                                                               When low, these                                     IFETCH/B                   signals indicate                                                               that an instruction                                                            OP code is being                                                               fetched.                                            BKG/FRGA   3       FO 75/40                                                                               When these signals are                              BKG/FRGB                   high,the UIOSM is                                                              processing an interrupt                                                        (running in background                                                         mode).                                              MROEB/     4       FO 75/40                                                                               When low, this signal                                                          indicates that MRR is                                                          being output on the                                                            address bus.                                        SC1B,SC2B, 4       FO 75/40                                                                               Outputs of the                                      SC4B, SC8          FO 20/11.25                                                                            State counter.                                   30.                                                                               MNTENB     4       FI 10/5.5                                                                              When low, this                                                                 line will tri-                                                                 state the outputs                                                              of the five                                                                    instruction decode                                                             PROMS.                                              SMOE/      4       FO 20423/                                                                              When low, this                                                         8.83    signal indicates                                                               that the stack                                                                 memory is being                                                                output on the I/O                                                              bus.                                                BSAOEX/BSBOEX                                                                             4       FO 47.75/9.81                                                                          When low, these                                                                signals indicate                                                               that byte A or B                                                               of the byte swap                                                               logic will be out-                                                             put on the I/O bus                                                             during the next                                                                clock.                                              SHAOEX/SHBOEX                                                                             4       FO 47.75/9.81                                                                          When high, these                                                               signals indicate                                                               that byte A or B                                                               of the shift logic                                                             will be output on                                                              the I/O bus during                                                             the next clock.                                     MRSVOEX/   4       FO 49/9.81                                                                             When low, this                                                                 signal indicates                                                               that the MRR save                                                              register will be                                                               output on the I/O                                                              bus during the next                                                            clock.                                              RCOEX/     4       FO 47.75/9.81                                                                          When low, this                                                                 signal indicates                                                               that the repeat                                                                counter will be                                                                output on the I/O                                                              bus during the next                                                            clock.                                              IIOAOEX/   4       FO 47.75/9.81                                                                          When low, this signal                                                          indicates that the most                                                        significant (A) byte of                                                        the I/O bus will be                                                            driven to all zeros                                                            during the next clock.                              PCLD/      4       FO 48/8.98                                                                             When low, this signal                                                          indicates that the                                                             program counter will be                                                        loaded from the I/O bus                                                        at the next clock.                                  STKOVF/    4       FO 25/12.5                                                                             This signal goes low                                                           during a CALL when this                                                        stack address is at                                                            maximum (15), or during                                                        a RETURN when the stack                                                        address is zero.                                    MRLD/      4       FO 3.75/4.75                                                                           When low, this signal                                                          indicates that MRR will                                                        be loaded from the I/O                                                         bus at the next clock.                           40.                                                                               REPEATB    4       FO 75/40                                                                               When high, this signal                                                         indicates that a repeat                                                        operation is in progress.                           MOPND/     4       FO 48/8.98                                                                             When low, this signal                                                          indicates that the memory                                                      data being read will be                                                        used during the next                                                           clock. This signal will                                                        be high for unused read                                                        data and during memory                                                         write cycles.                                       COND/      4       FO 173.75/                                                                             When low during a BRANCH,                                              12.47   CALL or RETURN, this                                                           signal indicates that                                                          the selected condition                                                         is true.                                            INVOP      4       FO 206.75/                                                                             When high this signal                                                  9.47    indicates that an                                                              invalid condition was                                                          detected in the state                                                          machine. Conditions                                                            that will cause this                                                           term to go high are:                                                           1.                                                                               RETURN with D3=0.                                                            2.                                                                               Repeat made with                                                               CALL, BRANCH,                                                                  RETURN, ICALL or                                                               IRETURN operators                                                            3.                                                                               GET or PUT with                                                                the state count                                                                greater than 1.                                                              4.                                                                               CALL, BRANCH,                                                                  RETURN, ICALL                                                                  and RETURN with                                                                the state count                                                                greater than 2.                                                              5.                                                                               ALU operators                                                                  other thau LOWD,                                                               STD, EI, OI, ADDC,                                                             SUBC and RSTK with                                                             the state count                                                                greater than 1.                                                              6.                                                                               Repeat made with                                                               the state count                                                                not equal to 1.                                                              7.                                                                               STWD or LDWD with                                                              D=0000.                                           ACBWE      4       FO 23.74/                                                                              When low, this signal                                                  12.18   indicates the "B"                                                              (low order) byte of                                                            the selected accumu-                                                           lator register is                                                              enabled for writing.                                ACWRITE/   4       FO 7.49/8.43                                                                           When low, this signal                                                          indicates that the                                                             selected accumulator                                                           is being written                                                               The "A" (high order.)                                                          byte is always written                                                         and the "B" (low                                                               order) byte is                                                                 controlled by the                                                              ACBWE/ signal.                                      STKA0      4       FO 22.48/11                                                                            Program stack address.                              STKA1                                                                          STKA2                                                                          STKA3                                                                          SMWEX/     4       FO 47.75/9.81                                                                          When low, this signal                                                          indicates that the                                                             program stack will be                                                          written from the I/O                                                           bus on the next clock.                              ENBREP/    4       FO 24/12                                                                               When low, this signal                                                          indicates a PUT to                                                             the repeat counter is                                                          taking place and a                                                             repeat operation will                                                          start on the next                                                              clock.                                              BYTSWPB    4       FO 75/40                                                                               When high, this                                                                signal indicates that                                                          the byte-swap bit is                                                           set.                                             50.                                                                               SCS0X      4       FO 47.75/9.81                                                                          These signals                                       SCS1X                      indicate that the                                                              shift function will                                                            be on the next clock:                                                          SCS0X SCS1X  function                                                          0     0      shift rt.                                                         1     0      no shift                                                          0     1      shift lft.                                                        1     1      double                                                                         shift lft.                             ALUMDX     4       FO 47.75/9.81                                                                          These signals indicate                              ALUS3X/    4       FO 47.75/9.81                                                                          what the ALU function                               ALUS2X/    4       FO 47.75/9.81                                                                          will be on the next                                 ALUS1X     4       FO 46.5/9.66                                                                           clock:                                              ALUX0X     4       FO 46.5/9.66                                                                           MD S3/                                                                               S2/                                                                               S1                                                                               S0                                                                               Func.                                                             1  0  0  1 1 F=A                                                               1  0  1  1 0 F=B                                                               0  0  1  0 1 F=A+B                                                             0  0  0  1 1 F=A-1                                                             0  1  1  0 0 F=A+1                                                             0  1  0  1 0 F=A-B                                                             1  0  1  1 1 F=A & B                                                           1  1  0  0 1 F=B/                                                              1  1  1  0 0 F=A/                                                              1  0  0  0 0 F=1's                                                             1  0  0  1 0 F=A or B                                                          1  1  0  1 0 F=A or B                                                          1  1  1  1 1 F=0's                                                             (F=ALU output,                                                                 A=Accumulator,                                                                 B=Memory.)                                          D3B        4       FO 75/40                                                                               These signals are copies                            F1B        4       FO 75/40                                                                               of instruction register                             F0B        4       FO 75/40                                                                               bits.                                               S2         4       FO 159.75/                                                                     11.47                                                       S1         4       FO 159.75/                                                                             (F=Function,                                                           11.47   D=Destivation,                                      SOB        4       FO 75/40                                                                               S=Source)                                           ACADR2     4       FO 17.48/9.36                                                                          Accumulator address.                                ACADR1     4       FO 17.48/9.36                                                                          When the state machine                              ACADR0     4       FO 17.48/9.36                                                                          internal clock is high                                                         the source accumulator                                                         address is present on                                                          these signals. When                                                            the clock is low the                                                           destination accumulator                                                        address is present.                                 IOBRCE/    4       FO      When low, this signal                                                          causes the I/O bus to go                                                       from transmit (output)                                                         to receive (input) mode.                                                       The signal may be driven                                                       from the foreplane with                                                        an open-collector driver                                                       to control the I/O bus                                                         for maintenance purposes.                           MRR/.A     3       FO 75/40                                                                               When low, these signals                             MRR/.B                     indicate that MRR is                                                           output on the address                                                          bus.                                             __________________________________________________________________________      *The Fanin (FI) or Fanout (FO) is expressed as H/L where H is the high         level FI or FO and L is the low level FI or FO. FI or FO is from the poin      of view of the UIOSM, and is expressed in standard TTL unit loads (40          μA high; and -1.6 mA low)                                                   Note:                                                                          Only one each of the following groups of signals will be active on the         foreplane at a time. Group A or B will be selected by jumper options for       use in a multipleprocessor environment. This allows memory/DMA logic to        recognize requests from two distinct state machines:                           1. BUSEN/A                                                                      BUSEN/B                                                                       2. IFETCH/A                                                                     IFETCH/B                                                                      3. BKG/FRGA                                                                     BKG/FRGB                                                                      4. MRR/.A                                                                       MRR/.B                                                                  

The following Tables XII and XII-A through G show the operators of the UIO State Machine

                  TABLE XII                                                        ______________________________________                                         UIO STATE MACHINE OPERATORS                                                    ______________________________________                                         NOTES:                                                                         (a)   The "M" bit is not listed under each operator since it                         always has the same meaning as earlier defined and                             actually appears in the instruction to which it applies.                 (b)   Additionally, the "C" bit is not listed under each                             operator, since it always has the same meaning as                              earlier defined.                                                         (c)   The following flags are conditioned by ALU operators:                    1.      The carry flag is only updated during ADD, SUBT,                               INCR, DECR, ADDC, AND SUBC operators.                                  2.      The ALU=0 flag is set if the output of the ALU                                 is all zero's.                                                         3.      The MSB flag is set if bit 15 of the I/O is zero.                      4.      The LSB flag is set if bit 0 of the I/O is zero.                       (d)   X = don't care                                                           ______________________________________                                    

                  TABLE XII-A                                                      ______________________________________                                         ARITHMETIC OP'S                                                                ______________________________________                                         1.  ADD     Places the results of a binary ADD of accumulator                              A(S) and memory into accumulator A(D), and/or into                             the memory reference register (MRR), or merely                                 updates the flag register (null). If the ADD over-                             flows, the carry flag will go true.                                F =        10                                                                  V =        00000                                                               D =        1[A (D)] Accumulator A(D)                                                      0001     Null                                                       S =        [A (S)]  Accumulator A(S)                                           2.  DECR    PLACES THE RESULTS OF MEMORY MINUS 1                                           INTO ACCUMULATOR A(D), AND/OR INTO                                             THE MEMORY REFERENCE REGISTER (MRR),                                           OR MERELY UPDATES THE FLAG REGISTER                                            (NULL). IF THE DECR UNDERFLOWS, THE                                            CARRY FLAG WILL GO FALSE.                                          F =        10                                                                  V =        00001                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        XXX                                                                 3.  INCR    PLACES THE RESULTS OF MEMORY PLUS 1                                            INTO ACCUMULATOR A(D), AND/OR INTO                                             THE MEMORY REFERENCE REGISTER (MRR),                                           OR MERELY UPDATES THE FLAG REGISTER                                            (NULL). IF THE INCR OVERFLOWS, THE                                             CARRY FLAG WILL GO TRUE.                                           F =        10                                                                  V =        00010                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        XXX                                                                 4.  ROTL    PLACES THE RESULTS OF A LEFT ROTATE BY                                         ONE BIT (MSB INTO LSB) ON ACCUMULATOR                                          A(S) INTO ACCUMULATOR A(D) OR MERELY                                           UPDATES THE FLAG REGISTER (NULL). THE                                          CARRY FLAG IS NOT                                                              AFFECTED.                                                          F =        10                                                                  V =        00011                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           5.  ROTR    PLACES THE RESULTS OF A RIGHT ROTATE                                           BY ONE BIT (LSB INTO MSB) ON ACCUMULATOR                                       A(S) INTO ACCUMULATOR A(D) OR MERELY                                           UPDATES THE FLAG REGISTER (NULL). THE                                          CARRY FLAG IS NOT AFFECTED.                                        F =        10                                                                  V =        00100                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           6.  SHFL    PLACES THE RESULTS OF A LEFT SHIFT BY                                          ONE BIT (ZERO SHIFTED INTO LSB) ON                                             ACCUMULATOR A(S) INTO ACCUMULATOR                                              A(D) OR MERELY UPDATES THE FLAG                                                (NULL). THE CARRY FLAG IS NOT                                                  AFFECTED.                                                          F =        10                                                                  V =        00101                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           7.  SHFM    PLACES THE RESULTS OF A LEFT SHIFT BY                                          ONE BIT -  (ZERO SHIFTED INTO LSB) ON                                          MEMORY INTO ACCUMULATOR A(D), AND/OR                                           INTO THE MEMORY REFERENCE REGISTER                                             (MRR), OR MERELY UPDATES THE FLAG                                              REGISTER (NULL). THE CARRY FLAG IS NOT                                         AFFECTED.                                                          F =        10                                                                  V =        00110                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        XXX                                                                 8.  SHFR    PLACES THE RESULTS OF A RIGHT SHIFT BY                                         ONE BIT (ZERO SHIFTED INTO MSB) ON                                             ACCUMULATOR A(S) INTO ACCUMULATOR A(D)                                         OR RAM, OR MERELY UPDATES THE FLAG REGISTER                                    (NULL). THE CARRY FLAG IS NOT AFFECTED.                            F =        10                                                                  V =        00111                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           9.  SUBT    PLACES THE RESULTS OF A BINARY                                                 SUBTRACT ON MEMORY AND                                                         ACCUMULATOR A(S) (MEMORY MINUS A(S))                                           INTO ACCUMULATOR A(D), AND/OR INTO                                             THE MEMORY REFERENCE REGISTER (MRR),                                           OR MERELY UPDATES THE FLAG REGISTER                                            (NULL). IF THE SUBT UNDERFLOWS, THE                                            CARRY FLAG WILL GO FALSE.                                          F =        10                                                                  V =        01000                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           10. DRTL    PLACES THE RESULTS OF A LEFT ROTATE BY                                         2 BITS ON ACCUMULATOR A(S) INTO                                                ACCUMULATOR A(D) OR RAM, OR MERELY                                             UPDATES THE FLAG REGISTER (NULL). THE                                          CARRY FLAG IS NOT AFFECTED.                                        V =        10111                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           ______________________________________                                    

                  TABLE XII-B                                                      ______________________________________                                         LOGICAL OP'S                                                                   ______________________________________                                         1.  AND     PLACES THE RESULTS OF A LOGICAL AND                                            ON ACCUMULATOR A(S) AND MEMORY                                                 (A * M) INTO ACCUMULATOR A(D), AND/OR                                          INTO THE MEMORY REFERENCE                                                      REGISTER (MRR), OR MERELY UPDATES                                              THE FLAG REGISTER (NULL). THE CARRY                                            FLAG IS NOT AFFECTED.                                              F =        10                                                                  V =        01001                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           2.  CMA     PLACES THE COMPLEMENT OF                                                       ACCUMULATOR A(S) INTO ACCUMULATOR                                              A(D) AND/OR INTO THE MEMORY                                                    REFERENCE REGISTER (MRR), OR MERELY                                            UPDATES THE FLAG REGISTER (NULL).                                              THE CARRY FLAG IS NOT AFFECTED.                                    F =        10                                                                  V =        01010                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           3.  CMM     PLACES THE COMPLEMENT OF                                                       MEMORY INTO ACCUMULATOR A(D),                                                  AND/OR INTO THE MEMORY REFERENCE                                               REGISTER (MRR), OR MERELY UPDATES                                              THE FLAG REGISTER (NULL).  THE CARRY                                           FLAG IS NOT AFFECTED.                                              F =        10                                                                  V =        01011                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        XXX                                                                 4.  ONES    SETS ACCUMULATOR A(D) AND/OR THE                                               MEMORY REFERENCE REGISTER (MRR) TO                                             ALL ONES OR MERELY UPDATES THE                                                 FLAG REGISTER (NULL). THE CARRY FLAG                                           IS NOT AFFECTED.                                                   F =        10                                                                  V =        01100                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        XXX                                                                 5.  OR      PLACES THE RESULTS OF A LOGICAL OR                                             ON ACCUMULATOR A(S) AND MEMORY                                                 (A + M) INTO ACCUMULATOR A(D), AND/OR                                          INTO THE MEMORY REFERENCE                                                      REGISTER (MRR), OR MERELY UPDATES                                              THE FLAG REGISTER (NULL). THE CARRY                                            FLAG IS NOT AFFECTED.                                              F =        10                                                                  V =        01101                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           6.  XOR     PLACES THE RESULTS OF A LOGICAL                                                EXCLUSIVE OR ON ACCUMULATOR A(S)                                               AND MEMORY (A EXOR M) INTO                                                     ACCUMULATOR A(D), AND/OR INTO THE                                              MEMORY REFERENCE REGISTER (MRR),                                               OR MERELY UPDATES THE FLAG REGISTER                                            (NULL). THE CARRY FLAG IS NOT                                                  AFFECTED.                                                          F =        10                                                                  V =        01110                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           7.  ZERO    SETS ACCUMULATOR A(D) AND/OR THE                                               MEMORY REFERENCE REGISTER (MRR) TO                                             ALL ZEROS OR MERELY UPDATES THE                                                FLAG REGISTER (NULL). THE CARRY FLAG                                           IS NOT AFFECTED. -                                                                 F =  10                                                        V = 01111                                                                      D = 1[A(D)] ACCUMULATOR A(D)                                                       0001    NULL                                                               S = XXX                                                                        8.  ADDC    PLACES THE RESULTS OF A BINARY ADD OF                                          ACCUMULATOR A(S), MEMORY, AND THE                                              CARRY FLAG INTO ACCUMULATOR A(D),                                              AND/OR INTO THE MEMORY REFERENCE                                               REGISTER (MRR) OR MERELY UPDATES                                               THE FLAG REGISTER (NULL). IF THE ADD                                           OVERFLOWS, THE CARRY FLAG WILL GO                                              TRUE.                                                              F =        10                                                                  V =        11100                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           9.  SUBC    PLACES THE RESULT OF A BINARY                                                  SUBTRACT ON MEMORY AND                                                         ACCUMULATOR A(S), LESS THE CARRY                                               FLAG, (MEMORY MINUS A(S) MINUS                                                 CARRY) INTO ACCUMULATOR A(D),                                                  AND/OR INTO THE MEMORY REFERENCE                                               REGISTER (MRR), OR MERELY UPDATES                                              THE FLAG REGISTER (NULL). IF THE SUBT                                          UNDERFLOWS, THE CARRY FLAG WILL GO                                             FALSE.                                                             F =        10                                                                  V =        11101                                                               D =        1[A(D)]  ACCUMULATOR A(D)                                                      0001     NULL                                                       S =        [A(S)]   ACCUMULATOR A(S)                                           ______________________________________                                    

                                      TABLE XII-C                                  __________________________________________________________________________     PROGRAM STACK OP'S                                                             __________________________________________________________________________     Note: THE FOLLOWING INSTRUCTIONS DO NOT AFFECT                                 CONDITION FLAGS.                                                               __________________________________________________________________________       BRANCH                                                                               IF THE CONDITION TEST IS TRUE, THE PROGRAM COUNTER                             (PC) WILL BE REPLACED WITH ACCUMULATOR A(S) OR WITH                            A LITERAL STORED IN MEMORY.                                                    F =                                                                               11                                                                          V =                                                                               10000   BRANCH UNCONDITIONALLY (OR NOT)                                        10001   BRANCH ON ALU = 0 (OR NOT)                                             10010   BRANCH ON ALU MSB = 0 (OR NOT)                                         10011   BRANCH ON ALU CARRY = 1 (OR NOT)                                       10100   BRANCH ON ALU LSB = 0 (OR NOT)                                         10101   BRANCH ON EXTERNAL FLAG 1 = 1 (OR NOT)                                 10110   BRANCH ON EXTERNAL FLAG 2 = 1 (OR NOT)                                 10111   BRANCH ON EXTERNAL FLAG 3 = 1 (OR NOT)                              D =                                                                               SXXF                                                                               S = 0                                                                              BRANCH ADDRESS IN MEMORY                                                   S = 1                                                                              BRANCH ADDRESS IN ACCUMULATOR A(S)                                         F = 1                                                                              EXECUTE ON CONDITION TEST TRUE                                             F = 0                                                                              EXECUTE ON CONDITION TEST NOT TRUE                                  S =                                                                               XXX     IF BRANCH ADDRESS IS IN MEMORY                                         [A(S)]  IF BRANCH ADDRESS IS IN ACCUMULATOR A(S)                      CALL  IF THE CONDITION TEST IS TRUE, THE PROGRAM COUNTER (PC)                        WILL BE REPLACED WITH ACCUMULATOR A(S) OR WITH A                               LITERAL STORED IN MEMORY, AND THE OLD PROGRAM                                  COUNT (+1 IF M=1, +2 IF M=0) WILL BE PUSHED INTO                               THE PROGRAM STACK. UP TO 16 CALLS CAN BE MADE                                  FROM THE INITIAL PROGRAM START POINT.                                          F =                                                                               11                                                                          V =                                                                               01000   CALL UNCONDITIONALLY (OR NOT)                                          01001   CALL ON ALU = 0 (OR NOT)                                               01010   CALL ON ALU MSB = 0 (OR NOT)                                           01011   CALL ON ALU CARRY = 1 (OR NOT)                                         01100   CALL ON ALU LSB = 0 (OR NOT)                                           01101   CALL ON EXTERNAL FLAG 1 = 1 (OR NOT)                                   01110   CALL ON EXTERNAL FLAG 2 = 1 (OR NOT)                                   01111   CALL ON EXTERNAL FLAG 3 = 1 (OR NOT)                                D =                                                                               SXXF                                                                               S = 0                                                                              CALL ADDRESS IN MEMORY                                                     S = 1                                                                              CALL ADDRESS IN ACCUMULATOR A(S)                                           F = 1                                                                              EXECUTE ON CONDITION TEST TRUE                                             F = 0                                                                              EXECUTE ON CONDITION TEST NOT TRUE                                  S =                                                                               XXX     IF CALL ADDRESS IS IN MEMORY                                           [A(S)]  IF CALL ADDRESS IS IN ACCUMULATOR A(S)                        RETURN                                                                               IF THE CONDITION TEST IS TRUE, THE PROGRAM COUNTER                             WILL BE REPLACED WITH THE LAST VALUE STORED IN THE                             PROGRAM STACK.                                                                 F =                                                                               11                                                                          V =                                                                               11000   RETURN UNCONDITIONALLY (OR NOT)                                        11001   RETURN ON ALU = 0 (OR NOT)                                             11010   RETURN ON ALU MSB = 0 (OR NOT)                                         11011   RETURN ON ALU CARRY = 1 (OR NOT)                                       11100   RETURN ON ALU LSB = 0 (OR NOT)                                         11101   RETURN ON EXTERNAL FLAG 1 =  1 (OR NOT)                                11110   RETURN ON EXTERNAL FLAG 2 = 1 (OR NOT)                                 11111   RETURN ON EXTERNAL FLAG 3 = 1 (OR NOT)                              D =                                                                               1XX1    EXECUTE ON CONDITION TEST TRUE                                         1XX0    EXECUTE ON CONDITION TEST NOT TRUE                                  S =                                                                               XX0                                                                   ICALL THIS INSTRUCTION IS FORCED BY HARDWARE TO ENTER                                INTERRUPT MODE. THE BACKGROUND FLAGS AND ACCUMULATOR                           ARE ACTIVE AFTER THIS INSTRUCTION IS EXECUTED. MRR IS                          SAVED IN THE MRR SAVE REGISTER AND THEN PC (PC IS                              INCREMENTED) IS STORED IN THE PROGRAM STACK. THE                               ADDRESS PROVIDED BY THE APPLICATION LOGIC ON THE                               I/O BUS IS LOADED IN PC.                                                       F =                                                                               11                                                                          V =                                                                               11111                                                                       D =                                                                               1111                                                                        S =                                                                               111                                                                         M =                                                                               1                                                                           C =                                                                               1                                                                     IRETURN                                                                              EXITS INTERRUPT MODE, RESTORES MRR, AND REPLACES                               THE PROGRAM COUNTER WITH THE LAST VALUE STORED IN                              THE PROGRAM STACK. THE FOREGROUND FLAGS AND ACCU-                              MULATORS ARE ACTIVE AFTER THIS INSTRUCTION IS                                  EXECUTED.                                                                      F =                                                                               11                                                                          V =                                                                               00XXX                                                                       D =                                                                               1XXX                                                                        S =                                                                               XXX                                                                   BCALL THIS INSTRUCTION ALLOWS ENTRY INTO BACKGROUND MODE                             FOR MAINTENANCE PURPOSES. BACKGROUND MODE IS                                   ENTERED AND PC+1 IS STORED ON THE STACK. THE                                   INSTRUCTION AT PC+1 IS THEN EXECUTED.                                          F =                                                                               11                                                                          V =                                                                               11111                                                                       D =                                                                               01111                                                                       S =                                                                               XX1                                                                 __________________________________________________________________________

                  TABLE XII-D                                                      ______________________________________                                         LOAD, STORE, AND MOVE OP'S                                                     ______________________________________                                         Note: The following instructions make reference to a                           memory operand word or source accumulator word                                 as (AB) where the left character (A) is the                                    high order byte and the right character (B) is                                 the low order byte. These instructions will                                    condition all flags except the carry flag.                                     ______________________________________                                         1.  RDW      (READ WORD) PLACES THE CONTENTS OF                                             MEMORY (AB) INTO ACCUMULATOR A(D)                                              AS AB, AND/OR INTO THE MEMORY                                                  REFERENCE REGISTER (MRR) AS AB, OR                                             MERELY UPDATES THE FLAG                                                        REGISTER (NULL).                                                         F =  10                                                                        V =  10000                                                                     D =  1[A(D)]         ACCUMULATOR A(D)                                               0001            NULL                                                      S =  XXX                                                                2.  RDB      (READ BYTE) PLACES THE CONTENTS OF                                             MEMORY (AB) INTO ACCUMULATOR A(D)                                              AS 0A IF THE BYTE SWAP BIT IS 0 OR AS 0B                                       IF THE BYTE SWAP BIT IS 1.                                               F =  10                                                                        V =  10001                                                                     D =  1[A(D)]         ACCUMULATOR A(D)                                               0001            NULL                                                      S =  XXX                                                                3.  RDBW     (READ BEFORE WRITE BYTE) PLACES THE                                            CONTENTS OF MEMORY (AB) INTO ACCUMULATOR A(D) AS AX IF THE                     BYTE                                                                           SWAP BIT IS 1 OR AS BX IF THE BYTE SWAP                                        BIT IS 0. THE X BYTE INDICATES THAT                                            THE DESTINATION ACCUMULATOR A(D)                                               IS UNCHANGED FOR THAT BYTE.                                              F =  10                                                                        V =  10010                                                                     D =  1[A(D)]         ACCUMULATOR A(D)                                               0001            NULL                                                      S =  XXX                                                                4.  RBWR     (READ BEFORE WRITE BYTE REVERSED)                                              PLACES THE CONTENTS OF MEMORY (AB)                                             INTO ACCUMULATOR A(D) AS AX IF THE                                             BYTE SWAP BIT IS 0 OR AS BX IF THE BYTE                                        SWAP BIT IS 1. THE X BYTE INDICATES                                            THAT THE DESTINATION ACCUMULATOR                                               A(D) IS UNCHANGED FOR THAT BYTE.                                         F =  10                                                                        V =  10110                                                                     D =  1[A(D)]         ACCUMULATOR A(D)                                               0001            NULL                                                      S =  XXX                                                                5.  SWAC     (SWAP ACCUMULATOR) PLACES THE                                                  CONTENTS OF ACCUMULATOR A(S) (AB) INTO                                         ACCUMULATOR A(D) AS BA.                                                  F =  10                                                                        V =  10011                                                                     D =  1[A(D)]         ACCUMULATOR A(D)                                               0001            NULL                                                      S =  [A(S)]          ACCUMULATOR A(S)                                          M =  1                                                                  6.  WRTW     (WRITE WORD) PLACES THE CONTENTS OF                                            ACCUMULATOR A(S) (AB) INTO                                                     ACCUMULATOR A(D) AS AB, AND/OR                                                 INTO THE MEMORY REFERENCE REGISTER                                             (MRR) AS AB, OR INTO RAM MEMORY AS                                             AB, OR MERELY UPDATES THE FLAG                                                 REGISTER (NULL).                                                         F =  10                                                                        V =  10100                                                                     D =  1[A(D)]         ACCUMULATOR A(D)                                               0000            RAM MEMORY                                                     0001            NULL                                                      S =  [A(S)]          ACCUMULATOR A(S)                                          M =  1                                                                  7.  WRTB     (WRITE BYTE) PLACES THE CONTENTS OF                                            ACCUMULATOR A(S) (AB) INTO                                                     ACCUMULATOR A(D) OR RAM MEMORY                                                 AS AB IF THE BYTE SWAP BIT IS 1 OR BA                                          IF THE BYTE SWAP BIT IS 0.                                               F =  10                                                                        V =  10101           ACCUMULATOR D(S)                                          D =  1[A(D)]         RAM                                                            0001            NULL                                                      S =  [A(S)]          ACCUMULATOR A(S)                                          M =  1                                                                  8.  LDWD     (LOAD WORD DIRECT) PLACES THE                                                  CONTENTS OF MEMORY INTO MRR. PLACES                                            THE CONTENTS OF MEMORY POINTED TO                                              BY THE NEW CONTENTS OF MRR INTO ACCUMULATOR A(D) (AB),                         AND/OR INTO                                                                    MRR, OR MERELY UPDATES THE                                                     FLAG REGISTER (NULL).                                                    F =  10                                                                        V =  11000                                                                     D =  1[A(D)]         ACCUMULATOR A(D)                                          S =  XXX                                                                9.  STWD     (STORE WORD DIRECT) PLACES THE                                                 CONTENTS OF MEMORY INTO MRR. PLACES                                            THE CONTENTS OF ACCUMULATOR A(S)                                               (AB) INTO RAM MEMORY AT THE ADDRESS                                            POINTED AT BY THE NEW MRR VALUE,                                               AND/OR INTO MRR.                                                         F =  10                                                                        V =  11001                                                                     D =  0001                                                                      S =  [A(S)]          ACCUMULATOR A(S)                                   10. RSTK     (READ STACK) PLACES THE CONTENTS OF                                            THE TOP WORD OF THE STACK (RETURN                                              ADDRESS) INTO ACCUMULATOR A(D).                                          F =  10                                                                        V =  11110                                                                     D =  1[A(D)]         ACCUMULATOR A(D)                                               0001            NULL                                                      S =  XXX                                                                ______________________________________                                    

                  TABLE XII-E                                                      ______________________________________                                         GET AND PUT OP'S                                                               ______________________________________                                         NOTE: The following instructions do not affect condition flags.                1.  GET     PLACES CONTENTS OF EXTERNAL REGISTER                                           R(N) OR THE REPEAT COUNTER INTO                                                ACCUMULATOR A(D), OR INTO RAM                                                  MEMORY. THE "C" BIT MUST BE 1 IN THE                                           INSTRUCTION. THE "M" BIT MUST BE 1                                             IN THIS INSTRUCTION.                                               F =        00                                                                  V =        [R(N)]         EXTERNAL                                                                       REGISTER R(N)                                        D =        1[A(D)]        ACCUMULATOR                                                                    A(D)                                                            0000           RAM MEMORY                                                      0001           NULL                                                 S =        XX0            APPLICATION                                                                    REGISTER                                                        XX1            REPEAT COUNTER                                       2.  PUT     PLACES CONTENTS OF ACCUMULATOR A(S)                                            OR MEMORY INTO EXTERNAL REGISTER                                               R(N). THREE SEPARATE "STROBE" LINES                                            CAN ALSO BE GENERATED FOR USE BY THE                                           APPLICATION DEPENDENT LOGIC. THE                                               CONTENTS OF ACCUMULATOR A(S) OR                                                MEMORY CAN ALSO BE COPIED TO THE                                               MEMORY REFERENCE REGISTER (MRR).                                   F =        01                                                                  V =        [R(N)]             EXTERNAL                                                                       REGISTER R(N)                                    D =        SFFF     S = 0     PUT FROM                                                                       MEMORY                                                               S = 1     PUT FROM                                                                       ACCUMULATOR                                                                    A(S)                                                                 FFF = 000 GENERATE STROBE                                                                #1                                                                   FFF = 001 GENERATE STROBE                                                                #2                                                                   FFF = 010 GENERATE STROBE                                                                #3                                                                   FFF = 011 LOAD AND ENABLE                                                                REPETITION                                                                     COUNTER                                          S =        XXX                IF PUT FROM                                                                    MEMORY                                                      [A(S)]             IF PUT FROM                                                                    ACCUMULATOR                                                                    A(S)                                             ______________________________________                                    

                  TABLE XII-F                                                      ______________________________________                                         MISCELLANEOUS OP'S                                                             ______________________________________                                         NOTE: The following instructions do affect condition flags.                    1.    EI     RESETS THE INTERRUPT MASK BIT.                                           F =  10                                                                        V =  11010                                                                     D =  0001     NULL                                                             S =  XXX                                                                2.    DI     SETS THE INTERRUPT MASK BIT.                                             F =  10                                                                        V =  11011                                                                     D =  0001     NULL                                                             S =  XXX                                                                ______________________________________                                    

                  TABLE XII-G                                                      ______________________________________                                         ALU OP CODE SUMMARY TABLE (F = 10)                                             ______________________________________                                         Note: This code summary table for the Function Variant                         Field V is listed in reference to:                                             Arithmetic Op's (Table XII-A)                                                  Logical Op's (Table XII-B)                                                     Load, Store, Move Op's (Table XII-D)                                           ______________________________________                                         V      V     V     V                                                           3      2     1     0       V4 = 0    V4 = 1                                    ______________________________________                                         0      0     0     0       ADD       RDW                                       0      0     0     1       DECR      RDB                                       0      0     1     0       INCR      RDBW                                      0      0     1     1       ROTL      SWAC                                      0      1     0     0       ROTR      WRTW                                      0      1     0     1       SHFL      WRTB                                      0      1     1     0       SFHM      RBWR                                      0      1     1     1       SHFR      DRTL                                      1      0     0     0       SUBT      LDWD                                      1      0     0     1       AND       STWD                                      1      0     1     0       CMA       EI                                        1      0     1     1       CMM       DI                                        1      1     0     0       ONES      ADDC                                      1      1     0     1       OR        SUBC                                      1      1     1     0       XOR       RSTK                                      1      1     1     1       ZERO      Reserved                                  ______________________________________                                    

Operational Factors

The external memory storage RAM 90 is used to hold programs which have to do with the transferring of data between the external memory 90, the microprocessor unit and the application dependent registers 60 where data can be transferred to selected peripheral terminals or received from selected peripheral terminals. While the application dependent register 60 can buffer and generally holds several words, it is also necessary that large batches of character transfers, such as a 1,000 character batch, will be temporarily stored or buffered in the external RAM memory 90. This is necessary since data transfers to and from the peripheral devices are very slow in comparison with the fast speed of operation of the microprocessor and the host computer.

It will be noted that the main host system 100 is connected by means of a message level interface bus 105 which, through a host adapter, not shown, connects to the application dependent registers 60. Further, as seen in FIG. 1 individual peripherals can be shown as items 109_(a) and 109_(b) which are connected to the external registers. Each of these peripherals also has an adapter unit 109_(c) which controls the peripheral terminal unit and can also be instructed by the microprocessor system through instruction words passed through application dependent registers 60.

As seen in FIGS. 2A and 2B the general control and coordination is handled by the instruction decoder-controller 23 which has connections to all of the units in the system; however, the main interconnections have been shown on the drawings which indicate control lines to the major units involved.

Since the basic function of the overall system is to control and effectuate the transfer of data between selected peripherals and the main host system, it is helpful to consult the data provided in the previously cited patents which were incorporated by reference. The system operation is initiated when the main host system 100 of FIG. 1 conveys an I/O descriptor command word on the message level interface lines 105, this command being placed into a selected application dependent register 60. As mentioned in the previously cited patent references, the main host system also provides a "descriptor link" word signal which identifies a task to be performed so that when the task is either completed or incompleted, the peripheral-controller can formulate a Result Descriptor word which can be conveyed to the main host system to inform it of the condition status as either completion or non-completion of the task to be performed and also to identify the task so that the result word data will be channeled to the proper memory location in the main host system where data concerning a given task has been located.

The microprocessor system is placed into operation by means of the "clear" signal shown in FIG. 2A at line 11, at which time it starts operations so that the first address of the program counter is used to address the program memory 50 in order to initiate the fetching and execution of instruction words.

The receipt of the I/O command descriptor word into the application dependent registers will cause the Interrupt line signal (on lines of bus 11) to be sent to instruction decoder-controller 23 whereby the microprocessor will fetch, analyze and execute operations as a result of the I/O command descriptor.

With the I/O descriptor in the application dependent register and with the Interrupt signal activated, the microprocessor will use a GET operator to get this command data from the application dependent register 60 and put it into a selected accumulator register 30 where it can then be read, analyzed and interpreted by the arithmetic logic unit (ALU 32) and its associated data manipulated circuitry so that the required operators and data will be sent again to the application dependent register 60, or the external memory 90 and such that the control logic 66 will permit the transfer of data to occur.

Assuming a Write operation (transfer from host computer system to peripheral), the I/O command descriptor from the main host system will have the address of a selected peripheral in its instructions. The address of this peripheral will also be taken on into a GET operation by the microprocessor and translated into an instruction which can then be put (PUT operation) into the peripheral (via an adapter) by using control logic 66 and selected application dependent registers 60 in order to select the desired peripheral device 109. As seen in FIG. 2 each of the peripheral devices will have an adapter 109_(c) which is associated with the peripheral device in order to control its operation and data transfers. Then the microprocessor can send appropriate instruction commands to the adapter unit of the selected peripheral such that the input line to the peripheral can be enabled and instructions can be provided by the microprocessor, for example, to take incoming data from the main host system 100 (which may be temporarily stored in the application dependent register 60 or temporarily stored in the external memory 90) and then transfer data to the selected peripheral terminal device.

For example, if the selected peripheral terminal device is a "card reader", then this peripheral unit is oriented to handle only one byte at a time so that it is then necessary for the microprocessor instructions to select only one byte at a time and to transfer the data one byte at a time from its storage in external memory into the peripheral terminal unit. On the other hand, if data, for example, is being transferred to a disk-type peripheral, which generally handles a two byte word (16 bits) then the data can be transferred in terms of "words" (symbolically designated AB) directly to the peripheral adapter and thence the peripheral disk.

Thus, it is seen that in certain situations it is necessary to select only one byte, at a time, out of a two byte word in order that one byte, at a time, can be transferred out into the peripheral which can only accept one byte at a time. In this case, if there is an accessed word AB composed of two bytes, it is then necessary for the microprocessor to select out one byte at a time for transfer to the peripheral. This is done generally by using the "low order" byte as the byte to be selected for transfer. Thus, in the word AB, the byte B would be selected for transfer to the peripheral, after which the word-byte positions AB would be byte-swapped into the word positions BA, and then the "low order" byte A could then be transferred into the peripheral terminal unit.

The I/O command descriptor may eventually wind up in a selected one of the accumulator registers 30 or in a selected external register 60 or in external memory 90. In any case it must be available from the host computer 100 so that the microprocessor can access it, analyze it and make the appropriate signals as to what further instructions must be generated.

The program counter 41 holds addresses which are used to select instruction data from the program memory 50. This program counter is reset to zero with the initiation of the "power on" signal and the clear signal.

With the initiation of the fetching of instruction words from the program memory and with the receipt of an I/O command descriptor, the command descriptor data will be transferred to an internal register of the microprocessor system, such as the accumulator register 30 where it can then be inspected and analyzed by the data manipulation circuitry (ALU 32) and the associated shift logic and byte swap circuitry 33, 34. Thus, the meaning and intent of the descriptor command can be translated into instructions for the selection of a peripheral device, through its adapter, and for a subsequent transfer of data to or from the particular peripheral terminal device.

For example, the PUT operator is generated by the microprocessor and is applied to the application dependent logic module 60_(L). An address (of a peripheral adapter and a peripheral terminal unit) will then be provided and the application dependent logic module will operate on this address to select the appropriate adapter and peripheral unit for data to be transferred. The software of the microprocessor system generates the PUT commands to the peripheral adapter.

When the microprocessor system generates a PUT operator to the application dependent logic module 60_(L), then this enables the system to operate such that the host computer will send data on message level interface 105 to selected application dependent registers 60 where it can then be transferred into and stored in the external memory 90. As the microprocessor system provides a multiple series of repeated GET operators, then each word of data (or each byte of data if the peripheral can only accept bytes) will be transferred from the external register 60 to the selected peripheral terminal.

Since the microprocessor operates much faster than the peripheral terminal, then what would generally be done is that if there is a multiple word transfer of data, is that the words would be stored in the external memory 90 and then fetched and transferred out to a selected peripheral at the slower speed with which the peripheral terminal device can accept the data. In this respect the external memory 90 acts as a storage buffer which permits the microprocessor to operate at its high speed while data can reside in the external memory 90 and then be transferred at a slower speed to the selected peripheral.

Data will be sent from external memory 90 to the peripheral terminal by the use of a PUT operator which is used to control the peripheral adapter and terminal unit. That is to say, the PUT operator will command a word to be transferred from external memory 90 into a selected external register 60 and thence the peripheral. The PUT operator always deals with full "words" (AB). For byte-oriented usage, the microprocessor generates intervening instructions to isolate a "byte" from a memory word into a selected accumulator from which a PUT operation is then executed.

The use of the memory reference register 40 is prominent here in that this register provides a source of addresses for the selection of operands and for the selection of programs which reside in the external memory 90.

In the situation of a Read operation where it is desired that a selected peripheral terminal unit will "send" data to the main memory of the host system, again the I/O descriptor command will be placed by the host computer into the application dependent register 60 which will then interrupt the microprocessor and ask it to "GET" the I/O command and to analyze and execute it. Since this is a Read operation from a selected peripheral device, the microprocessor will then generate the addresses and the transfer commands so that a particularly selected peripheral and its control adapter will be selected and the data from that particularly selected peripheral will be transferred to application dependent register 60 and thence stored temporarily in external memory 90. Then a series of GET operators will cause the transfer of the words stored in external memory 90 to the external register 60 and thence through the message level interface 105 over to the host system 100. Transfers to the host system will be done on a full word (two byte) basis, AB, in repetitive cycles since the host system can accept the complete 16 bit word AB.

In summary, a multiple number of GET operators will cause the transfer of data from the peripheral terminal unit into the external memory 90 which acts as a buffer. Then a multiple number of PUT operators will be used to transfer this data from external memory 90 to the application register 60 and thence through the message level interface to the main host system 100. The adapters 109_(c) of FIG. 1 which are supplied for each of the peripheral devices are useful in accepting commands and for controlling operations of the particular peripheral. For example, at certain times it might be necessary to rewind the tape mechanism of a tape peripheral terminal unit or to eject or slew the paper on a printing device type terminal unit, or to select a certain address sector in the disk terminal unit.

Referring to FIGS. 15A, B, C, D, there is seen a simplified diagram at the upper right which shows the UIO state machine 1 controlling a block 60_(L) called the application dependent logic module. Attached to the application dependent logic module on a two way communication and bus arrangement is a series of devices which may be peripheral devices 109 and also the host computer 100 (which can be treated just like a peripheral device). Here the UIO state machine processor 1 controls the transfer of data between the host 100 and a peripheral device 109 or between a peripheral device and the host. The application dependent logic module 60_(L) provides control logic 66 (FIG. 2A) plus a series of external registers 60 plus a RAM memory 90 (often called external memory). In FIGS. 2A, 2B the control logic is item 66, the external registers (also called application dependent registers) are item 60 and the "external" RAM memory is item 90. Connected to the external registers 60 are a series of peripheral devices 109 or similarly a host computer 100.

The RAM memory 90 is addressed by a memory address bus 16 which comes from the memory reference register 40. It may be noted that there is a two way communication from the I/O bus and the external registers 60, while on the other hand there is only a one way communication from the I/O bus 10 over the RAM memory 90, since the output of the RAM memory 90 is conveyed on the memory output bus 12.

In FIG. 2B the controller registers 37 and 38 are really nothing more than an extra set of external registers but which happen to be placed on the UIO state machine processor because there was availability of space on the printed circuit board.

It may be noted that Universal Processor 1 is seen in FIG. 2A as having ALU 32, a shift logic 33 and byte swap circuit 34 which are used in order to do the work of editing, to add on headings and trailer information in addition to doing such things as translation from EBCDIC over to ASCII, etc.

The RAM memory 90 (in FIGS. 2B, 15A, B, C, D) will have two separate areas, one in which raw data is accepted and then after the data is taken out and "processed" through the state machine processor 1 it is put back in another portion of memory 90 which temporarily holds "processed" data or "translated" data. From here it is transferred to the external registers 60 for subsequent further transmission to either one of the peripheral devices or the host computer which appears as a peripheral to the application dependent logic module 60_(L).

The control logic 66 in FIG. 2A of the application dependent logic module 60_(L) has an address decoder (66_(ad) in FIG. 2) which is "hardware" and which is made to recognize any address involving the RAM memory 90 or the external register 60, since these are "slow" devices in relation to the high speed data handling of the universal processor 1. This recognition indicates that these two devices, that is the RAM memory 90 and the external registers 60, are both "slow" devices in relationship to the speed of the UIO processor. As a result, the control logic 66 will generate a WAIT signal (FIG. 2) which is sent to the instruction decoder-controller 23 of FIG. 2A whereby data in the state machine processor 1, when it is placed on the I/O bus 10, will be delayed before it can be transferred to an external register 60 or to the RAM memory 90. Thus, the memory 90 and external registers 60 operate as a buffer to hold data and the transfer of data into these elements is slowed down to meet the slow acceptance requirement of these elements.

The peripherals 109 will indicate when they are ready to accept data from the external registers 60 and will do so at a speed acceptable to the peripherals 109. Each time a peripheral 109 accepts a word or byte of data from the external registers 60, then there is left an empty space in the external registers 60 for the insertion of another word coming from the UIO state machine processor 1.

In the present described embodiment, the "slow" devices are actually the external RAM memory and the external register means, since these devices cannot accept data at the high speed rate of the I/O processor system--thus some means must be provided to recognize these slow devices so that the processor will be slowed down in its transfer rate.

However, it can be observed that this system may also connect to very fast devices, in which case there would be no need for slowing down the output transfer rate of the I/O processing means. Thus is the reason that there must be a differentiation in the address decoder of the application dependent logic module. It must be able to tell when slow devices are being addressed as distinguished from high speed devices being addressed which are capable of accepting the rapid transfer rate.

There are three phases of data transfer communications that occur in the system. These are phases I, II and III.

FIRST PHASE--I (FIGS. 15A AND 2)

This is the transfer of data from the host computer 10 over to the RAM memory 90 (slow memory). The data goes from the peripheral (host 100) over to the external register 60--from there it is transferred to the I/O bus 10 through the universal processor 1 and thence, via bus 10, is placed into the RAM memory 90. Similarly, the data is transferred from the peripheral 109 (via 109_(c)) over to external register 60 and thence to the I/O bus 10 and conveyed to the accumulator means 30 (FIG. 2A). Thence it is passed to the ALU 32 and through circuits 33 and 34 over to the I/O bus 10 again and thence to the RAM memory 90. When the data was passed through the ALU 32 and circuits 33 and 34, it could have been translated, edited, shifted or processed in any number of ways, including "no processing" at all, where it could have just been passed straight through without processing.

SECOND PHASE--II (FIGS. 15B AND 2) Editing the data in the RAM 90

Here the data goes from RAM memory 90 over the memory-out bus 12 over to the memory operand register 31 (FIG. 2A) and to the ALU 32 and thence through circuits 33 and 34 to the I/O bus 10 over to the accumulator registers 30. Here the data is taken from the accumulator registers 30 back through elements 32, 33 and 34 over to the I/O bus 10 from whence it is passed on to the RAM memory 90. This operation may occur several times, whereby the data passes through the UIO state machine 1 several times for different elements of processing.

The WAIT signal kicks in when there is recognition by the address decoder 60_(ad) (FIG. 2) in the control logic 66 that the RAM memory 90 or the external register 60 is being addressed.

Thus, since it is not possible to address and transfer data to 90 and 60 in one clock (which is generally the case since these are slow units compared to the speed of the universal processor), then it is necessary that the control logic use its address decoder 66_(ad) to detect the address (of a slow unit) and then activate the WAIT line. There are two conditions here:

(a) the WAIT line is activated, or

(b) the WAIT line is not activated--which occurs in those cases where the "external unit" is a fast unit which can accept data at the high speed of the processor.

In the present case, both memory 90 and external registers 60 are "slow" units and take longer than one microsecond (one clock) in order to be accessed by a selective address and enable memory area availability for the insertion of, or access of, data.

If the peripherals such as 109 are "slow units", then a delay operation can be effectuated simply by using software loops.

THIRD PHASE--III (FIGS. 15C AND 2A)

This is data transfer from the slow RAM memory 90 to a "peripheral" (which may be either the host computer 100 or the peripheral device 109).

(a) Path No. 1--data travels on the memory-out bus 12 over to the arithmetic logic unit ALU 32 and circuits 33 and 34. Thence it travels on the I/O bus 10 over to the external register 60. From external register 60, the data is transferred to the peripheral unit 109 or else the host 100.

(b) Path No. 2 (FIG. 15D)--the data goes from the RAM memory 90 over to the external register 60 (DMA or direct memory access line). Then the data in the external register 60 is conveyed to the peripheral device 109 accordingly as the peripheral device is ready to accept a data word or a series of data words. The DMA or direct memory access is done by one command from the UIO processor unit 1 and there is no need to use a special command for each single word that is transferred.

Thus, the state machine universal processor 1 controls the application dependent logic module 60_(L). The application dependent logic module has two-way bus connections 105 to the host computer 100 and to the peripheral devices 109 via bus 105_(P). The application dependent logic module 60_(L) provides means to recognize when a slow device is addressed, so that it can then momentarily disable the system clock of the universal state machine processor 1 which delays the strobing of the I/O bus 10, which will cause a delay in transfer of data into the RAM memory 90 or into the external registers 60. Thus, the application dependent logic module acts as a device which "adjusts" the rapid transmission of data from the universal state machine processor to the slow acceptance of data by the RAM memory 90 and/or the external registers 60.

In regard to the "C" bit previously discussed under the title "C field", this feature permits certain economies in the number of instructions.

Because there is only one memory reference register (MRR), loops of code which deal with multiple address ranges, such as a loop to move `n` words from address `s` to address `d`, involve alternately loading MRR with source (`s`) and destination (`d`) addresses. Such loops also involve incrementing the `s` and `d` addresses for each iteration. Without the copy (C) bit, such a loop looks like:

    ______________________________________                                         <get # of words in accumulator A.sub.0 >                                       <get source address `s` in A.sub.1 >                                           <get destination address `d` in A.sub.2 >                                      L:  WRTW     MRR, A.sub.1                                                                             % MRR ←Source address                                  RDW      A.sub.3, M                                                                               % A.sub.3 ←Next source word from                                          memory                                                      ADD      A.sub.1, A.sub.1, 1                                                                      % Increment source address for next                                            time                                                        WRTW     MRR, A.sub.2                                                                             % MRR←Destination address                              WRTW     M, A.sub.3                                                                               % Store source word into memory                                                from A.sub.3                                                ADD      A.sub.2, A.sub.2, 1                                                                      % Increment destination address for                                            next time                                                   ADD      A.sub.0, A.sub.0, -1                                                                     % Decrement word counter A.sub.0                            BR       L, NZERO  % Go back to point L if not done                                               (A.sub.0 ≠0)                                      Total for loop = 8 instructions per word moved                                 ______________________________________                                    

Using the copy bit it is possible to combine the incrementing of the address accumulator with the setting of MRR in one step. To do so, adopting the trick of starting with `s-1` and `d-1` in the accumulators, this is done only once:

    ______________________________________                                         <get # of words in accumulator A.sub.0 >                                       <get source address `s` in A.sub.1 >                                           <get destination address `d` in A.sub.2 >                                      not         ADD      A.sub.1, A.sub.1, -1                                                                    % A.sub.1 now contains s-1                       inside                                                                         loop        ADD      A.sub.2, A.sub.2, -2                                                                    % A.sub.2 now contains d-1                       L:      ADD      A.sub.1, A.sub.1, 1, C                                                                    % increment source                                                             address and copy to MRR                                    RDW      A.sub.3, M % A.sub.3 ←next source word                                               from memory                                                ADD      A.sub.2, A.sub.2, 1, C                                                                    % increment destination                                                        address and copy to MRR                                    WRTW     M, A.sub.3 % write source word into                                                       memory from A.sub.3                                        ADD      A.sub.0, A.sub.0, -1                                                                      % decrement word                                                               counter A.sub.0                                            BR       L, NZERO   % go back to point L if                                                        not done (A.sub.0 ≠  0)                      Total for loop = 6 instructions per word moved                                 ______________________________________                                    

Thus, it is possible to save ((8-6) * n)-2 instructions by using move `n` words, or 2n-2 instructions. For 100 words, this is 198; at current speeds that equals about 50 microseconds saved for 100 words moved.

Byte Oriented Read/Write Operators

As was previously discussed, the UIO-SM has been implemented with several operators to simplify the processing of byte-oriented data even though the memory is organized in words which are two bytes wide. These particular operators work in conjunction with the memory reference register 40 of FIG. 2 which addresses external RAM data memory 90.

The byte-oriented read/write operators use the "byte-swap" feature of the UIO-SM such that the "desired" byte is always read from external memory (90) into the "low order" byte of a selected register of the destination accumulator A(D) even though the desired byte might have been in the "high" order byte of the memory location in 90. The desired byte, after being placed into the destination accumulator A(D), can then be processed. After the low order byte is processed, the high order byte of the accumulator A(D) must be updated with the other byte from the current data memory location, and then the two bytes are written into memory 90 as one word, and each byte will go into the proper position. This would be needed, for example, when a card reader peripheral is supplying only one byte of a word for each transfer operation.

In the case of byte-oriented operators, the decision whether or not to "byte-swap" is determined by the low order bit of the memory reference register 40 which, in essence, is a byte-address. The following Table XIII is an example which illustrates the use of these operators in handling sequential byte data which is stored in memory 90.

The next following Table XIV shows a sequence of instructions and the resultant signals in the memory reference register 40, the accumulator register 30 and the data memory 90. Thus, the sequence shown in Table XIV starts with loading the memory reference register 40; reading the byte (RDB); translation; read before write byte (RDBW); write byte (WRTB); incrementing the memory reference register (MRR 40); again read byte (RDB); again translate; again read before write byte (RDBW); write byte (WRTB); incrementing memory reference register 40; read byte (RDB); translate; read before write byte (RDBW); write byte (WRTB); and so on.

                  TABLE XIII                                                       ______________________________________                                         HANDLING SEQUENTIAL BYTE DATA                                                                     Memory                                                      Data Memory        Data                                                        Address            (MSB.sub.v -LSB.sub.v ***)                                  ______________________________________                                         0                  A        B                                                  1                  C        D                                                  2                  E        F                                                  ______________________________________                                          Sequential Data to be Processed = ABCDEF?                                      *Actually, the first UIOSM instruction must be in address zero if there i      no physical separation between program memory and data memory.                 **MSB = Most Significant Byte, LSB = Least Significant Byte                    Note:                                                                          the symbols ABCD here refer to successive bytes of memory data to be           processed in sequence.                                                   

                                      TABLE XIV                                    __________________________________________________________________________     EXEMPLARY SEQUENCE OF INSTRUCTIONS                                                                ACCUMULATOR DATA                                                                             MEMORY DATA                                   INSTRUCTION                                                                             MRR MRRLSB*                                                                              (MSB.sub.y -LSB.sub.y ***)                                                                   (MSB.sub.y -LSB.sub.y ***)                    __________________________________________________________________________     Load MRR with                                                                           0   0                                                                 starting addr                                                                  of seq. data                                                                   RDB                0      A                                                    process (translate)                                                                               X       A'                                                  RDBW               B       A'                                                  WRTB                              A'  B                                        increment MRR                                                                           0   1                                                                 RDB                0      B                                                    process (translate)                                                                               X       B'                                                  RDBW                A'     B'                                                  WRTB                              A'   B'                                      increment MRR                                                                           1   0                                                                 RDB                0      C                                                    process (translate)                                                                               X       C'                                                  RDBW               0       C'                                                  WRTB                              C'  D                                        etc.                                                                           __________________________________________________________________________      *MRRLSB = MRR Least Significant Bit. This bit does not address memory but      is used by the UIOSM to determine whether or not to byte swap on byte          oriented op's.                                                                 **MSB.sub.y = Most Significant Byte, LSB.sub.y = Least Significant Byte  

A further "byte-oriented" operator has been implemented into the UIO-SM and is illustrated in the following Table XV. This operator aids in the formation of a "two-byte" data word where the two bytes are sequentially located in data memory 90. But unless several OP's are used, it is not known whether or not the two desired bytes are in a single memory location or whether they straddle two memory locations.

The upper portion of Table XV shows the arrangement of data in a first Memory 1 and a second Memory 2 corresponding to true and false signals of the data memory address. Then the lower part of Table XV shows an exemplary sequence for the sequential instructions with reference to data in the memory reference register 40 and in the accumulator 30.

                  TABLE XV                                                         ______________________________________                                                     Memory         Memory                                              Data Memory Data 1         Data 2                                              Address     (MSB.sub.y -LSB.sub.y **)                                                                     (MSB.sub.y -LSB.sub.y **)                           ______________________________________                                         0           B        C         A      B                                        1           D        E         C      D                                        Desired Sequential Data = CD                                                                              ACCUMULATOR                                                                    DATA                                                INSTRUCTION MRR MRRLSB*    (MSB.sub.y -LSB.sub.y **)                           ______________________________________                                         Memory Data 1 Case:                                                            load MRR with                                                                              1        0                                                         data ending                                                                    address                                                                        RDB                            0      D                                        decrement MRR                                                                              0        1                                                         RBWR                           C      D                                        Memory Data 2 Case:                                                            load MRR with                                                                              1        1                                                         data ending                                                                    address                                                                        RDB                            0      D                                        decrement MRR                                                                              1        0                                                         RBWR                           C      D                                        ______________________________________                                          *MRRLSB = MRR least significant bit. This bit does not address memory but      is used by the UIOSM to determine whether or not to byte swap on byte          oriented OP's.                                                                 **MSB.sub.y = Most significant byte. LSB.sub.y = least significant byte  

Linear Micro-Sequencing

FIG. 2C is a schematic block drawing of the Instruction Decoder 23 with its linear micro-sequencing circuit. A State Counter 23_(s) is initiated into a Fetch operation upon receipt of a Clear signal to its input. The State Counter 23_(s) feeds address bits to the PROM 23_(p) which contains a set of internal micro-instructions. The PROM 23_(p) provides one output line designated Count Enable which is used to sequence the State Counter 23_(s).

One set of instruction signal outputs, selected from PROM 23_(p), are a set of control terms which are conveyed to a pipeline register 23_(r) which provides control signals to the units of the microprocessor and the application dependent logic 60_(L). The pipeline register 23_(r) is used (a) to synchronize the output control term signals and also (b) to delay (by one clock) an output control term so that the signal from PROM 23_(p) will be adequately stabilized. Another set of control signal terms are provided directly from the output lines of PROM 23_(p).

As seen by the dotted lines above PROM 23_(p), an alternate plug-compatible PROM 23_(x) can replace 23_(p) and be utilized by up to two extra address lines from State Counter 23_(s). Each line (1 bit) will permit the addressing of an alternate or added set of instructions from PROm 23_(x) (in addition to using the original 2 bit lines).

In FIG. 2C the Instruction Register 22 provides input instructions to PROM 23_(p). An input of 15 bits (instruction fields) is fed to Instruction Register 22 from either Program Memory 50 or external memory 90 depending on which memory has been selected as a source of data.

One register of Instruction Register 22 is dedicated to receipt of the one bit of data called the "M" bit which is placed in each instruction word (from Program Memory 50). As discussed earlier, this field (M) is the one which selects either the Program Counter 41 or the Memory Reference Register 40 as the source of addresses to be next used for the selection of data.

In FIG. 2C the Condition Select Multiplexer 23_(m) has inputs from internal flag registers 35, 36, and from external flags 23_(e) in the Application Dependent Logic 60_(L). The output of Condition Select Multiplexer 23_(m) is used to provide an input to PROM 23_(p) of the linear micro-sequencer. Operationally, it should be noted that, at the same time that an instruction is being decoded, there is simultaneously a Fetch of the operand, since the M bit, when set, will initiate selection of an address from Memory Reference Register 40 (or when M not set, selects Program Counter) to access data from a location in external memory 90 (or Program Memory 50).

FIG. 2C-1 is a schematic illustration indicating modes of the State Counter 23_(s). At state number 0 (upon activation of the Clear signal) a Fetch operation is initiated. Thence the "1" state is achieved where the instructions may start execution of an instruction.

After completion of the "1" state, the sequencer may return to "0" for a Fetch and proceed to the "2" state. Here an operation step can occur.

After completion of this cycle, the State Counter returns to "0" for another Fetch operation, or else sequence to state "3" which permits an additional set of operations as shown in FIG. 2C-1.

After this, State Counter goes to "0" (or "4") for Fetch.

The remaining portions of FIG. 2C-1 showing the states "4", "5", "6" and "7" refer to the situation in FIG. 2C where an alternate larger instruction PROM 23_(x) has been used to replace 23_(p) with the extra two address lines of 1 bit each for addressing the micro-instruction PROM. Here, an alternate instruction set can be accessed and sequenced, similar to the sequencing of the PROM 23_(p) using the states 0 through 3. The State Counter 23_(s) can thus be used to address and select instructions from either PROM 23_(p) or from a larger PROM 23_(x).

Referring again to FIG. 2C, the Instruction Register 22 is seen to provide a 5 bit address line to select an external register 60. There is further provided a 3 bit "source address" line and a 3 bit "destination address" line to Multiplexer 30_(x) (which is shown again in FIG. 2D). Referring to FIG. 2D, the accumulator registers 30 are seen clocked by a 8 megahertz clock, and also have a Write Enable (WE) input line coming from decoder-controller 23.

Multiplexer 30_(x) (FIG. 2D) receives input addresses (from instruction register 22) for the source of data and for the destination of data. The SELECT line to MUX 30_(x) enables the source address to be read on the first half of the clock as seen in FIG. 2E at "Read", and enables the destination address to be written on the second half of the clock at "Write". Thus, the source location of data to be processed, and the destination location, where the data is to be placed, are all accomplished in one clock (125 nanoseconds).

Referring to FIG. 2D, a latch 30_(t) is provided to the accumulator registers 30 to hold and convey data to ALU 32. The other data input to ALU 32 is from Memory Operand Register 31 which receives data and instructions along instruction bus 15 (from Program Memory 50), and/or memory data bus 12 (from external memory).

The I/O bus 10 provides a path for processed data to be fed back to accumulator registers 30 or to the external memory 90 or to the external registers 60 (of application dependent logic unit 60_(L)).

Referring to FIG. 2F, there is seen a schematic drawing showing the intercooperation of the Repetition Counter 42 and Repeat Mode Flip-Flop 23_(f) and decoder-controller 23.

When a LOAD/PUT OP occurs which loads a number N into the Repetition Counter 42, this operation also sets the Repeat Mode Flip-Flop 23_(f) which then continues to signal the decoder-controller 23 to continue iterative operations of the next instruction OP. On each iteration, the Repetition Counter is decremented. When the count therein reads "0", then a reset signal is conveyed to the Repeat Mode Flip-Flop 23_(f) to turn it off which will signal the decoder-controller 23 that the iteration is finished (or to be halted), at which time the microprocessor will then select the next instruction from Program Memory 50 (via program counter 41).

In FIG. 2F, there will be seen another line for resetting (shutting off) the Repeat Mode Flip-Flop 23_(f). This is done by using a HALT/REP signal from Control Logic 66 in the Application Dependent Logic Unit 60_(L). This could occur because Control Logic 66 has sensed an early ending in the data transfer operation.

The linear micro-sequencer enables functions to be partitioned among the various PROMs so that each PROM will handle certain functions. There is no need for a stack memory or a next address register in the micro-sequencing circuitry. The micro-sequencer lowers the need for multiple IC's and permits expansion of PROM usage with no increase in hardware.

The microprocessor system permits simplicity and time-economy with which instructions can be fetched and executed, and data fetched and manipulated for data transfer purposes can be accomplished by what may be called (1) instruction pipelining and (2) operand pipelining.

Certain overlapping operations are made to occur which provide for an exceptionally short time for instruction and operand fetch and for execution of instructions.

Thus, while the processor is fetching an instruction in one clock, on the next clock, it is storing the result data in an I/O (peripheral) device by means of the I/O bus 10, or it may be storing the result data in the external memory 90, for example. At the same time that the result data is being stored, another fetch cycle occurs which is a fetch cycle using a memory address on the address bus 16 which will then provide an output of memory data on the memory data bus 12.

Note that the external memory read path 12 is set separate from the memory write path 10 and the system can store the result data in a peripheral I/O device while at the same time reading instructions from memory.

There are basically two different lines or separate paths, one for instructions and one for operands. For example, the instruction bus 15 feeds instructions to the instruction register 22. The memory operand register 31 also can receive operands from the memory data bus 12. Thus, on one clock the instruction bus can feed instructions to the instruction register (and then to instruction decoder-controller) while on the next clock the operand can be fed to the memory operand register 31 to facilitate the execution of the instructions.

Since the address of the I/O device (peripheral) is contained in the instruction word, the system can immediately store data in the I/O device. One level of the instruction pipelining includes (a) storing result data into the internal register files (as the accumulators 30 or the external registers 60) and (b) storage of results into an I/O port adapter which connects to peripheral devices.

The operand pipeline uses the M bit. Thus, in one clock while the processor is storing result data by using the I/O bus and using an address that has already been fetched, then at the same time an instruction fetch cycle can be occurring from program memory 15, on the next clock a decoding operation takes place simultaneously with the fetching of the operand after which on the next clock the storage of result data takes place in an addressed location.

The M bit is used as part of the operand pipeline in order to determine which source of addressing will be used--that is whether the memory reference register 40 will be used (data pointer) or whether the program counter 41 will be used (instruction pointer). Please refer to page 76 of specification on Byte oriented Read/Write operators. Note that the arithmetic logic unit 32 has the one input from the memory operand register 31 while the other input is from the accumulator registers 30.

While a preferred embodiment of the disclosed invention has been described and explained, it is, of course, understood that modifications and changes may be made without departing from the concept of the invention as defined by the following claims. 

We claim:
 1. In a network providing a basic clock signal to an I/O processor means, where an I/O Processor System controls data transfers between a main host computer and a peripheral terminal, and wherein data being transferred is edited and processed by said I/O processor system at a faster rate than it can be accepted by an attached application dependent logic module, the I/O Processor System comprising:(a) I/O processor means for controlling an application dependent logic module, and I/O processor means including:(a1) means for accessing data-in-transit in said application dependent logic module and processing said data for return to said application dependent logic module; (a2) means, responsive to a wait-delay signal from said application dependent logic module, for slowing the data transfer rate from said I/O processor means to an external register means and to an external RAM memory means, said external register means and said external RAM memory means functioning to temporarily store data-in-transit within said application dependent logic module; said means for slowing including:(a2a) delay circuit means having a first said basic clock signal input and said second wait-delay signal input for providing a processor clock output signal for clocking said I/O processor means; (b) said application dependent logic module for providing data transfers between said main host computer and said peripheral terminal, said application dependent logic module including:(b1) said external register means connected to said main host computer and to said peripheral terminal for temporary storage of data-in-transit; (b2) said external RAM memory means connected to said I/O processor means and to said external register means, said RAM memory means for temporary storage of data before and after processing by said I/O processor means; (b3) and wherein said external register means and said external RAM memory means is only capable of accepting data at a rate slower than the output data rate capability of said I/O processor means; (b4) means to sense when said external register means and/or said external RAM memory means is addressed by said I/O processor means; (b5) means, responsive to said means to sense, to generate said wait-delay signal to said I/O processor means, said wait-delay signal operating to slow the transfer rate of data from said I/O processor means to said external register means or to said external RAM memory means.
 2. In a data transfer network for transferring data between a main host computer and a plurality of peripheral devices wherein a universal processor means, having a basic clock signal, cooperates with an application dependent logic module to effectuate said data transfers, a system for facilitating rapid transfer of data from the said universal processor means with the slow speed of an external RAM memory means and external register means in the application dependent logic module which temporarily buffers data going to and from peripheral devices and the main host computer, the system comprising:(a) universal processor means for controlling an application dependent logic module; (b) an application dependent logic module which includes an external register means and a RAM external memory means wherein said register means and memory means are devices which operate slower than the said universal processor means and wherein said application dependent logic module includes:(b1) means to sense when an address is directed to said RAM external memory means or to said external register means; (b2) means to generate a WAIT signal upon the sensing of such an address; (b3) means to connect said WAIT signal to said universal processor means to delay the said basic clock signal operating on said universal processor means; (c) and wherein said universal processor means includes:(c1) means to generate an address and data for data transfer onto an I/O bus for receipt by said external RAM memory means and said external register means; (c2) means to generate strobe signals on said I/O bus; (c3) said I/O bus connecting said processor means to said application dependent logic module and to said RAM external memory means and said external register means; (c4) instruction decoder-controller means for receiving said WAIT signal and for delaying the strobing of said I/O bus; (c5) auxiliary processing means for editing, translating and processing data taken from said RAM memory means and returned to said RAM memory means; (c6) means to select instructions from an internal PROM memory means in said universal processor means or to select instructions from said external RAM memory means for application to said instruction-decoder controller means; (c7) said internal PROM memory means for storing instructions for data-transfer operations, said instructions being addressed and accessed by said means to select instructions.
 3. An I/O subsystem, which receives a basic clock signal, for managing data transfers between a host computer and one or more peripheral terminals, said I/O subsystem comprising:(a) I/O processing means operating in cooperation with an application dependent logic module for controlling data transfers and for editing, translating, and processing data-in-transit, said I/O processing means including:(a1) internal arithmetic logic circuitry means to process data in transit according to instructions from an internal PROM memory; (a2) said internal PROM memory holding instructions for data transfers and data processing, and connected to supply said instructions to an instruction decoder-controller; (a3) an instruction decoder-controller for operating said arithmetic logic circuitry means according to instructions received from said internal PROM memory, said instruction decoder-controller including:(a3-1) delay-clock circuit means having a first input from said basic clock signal and a second input from said WAIT signal for providing an output clock signal for clocking said I/O processing means, said WAIT signal being received from an address-decoder means, said delay-clock circuit means operating to regulate the transmission rate of data to or from said I/O processing means; (a4) memory address logic means for generating address data for transmittal on a memory address bus; (a5) means for storing data and instructions to be addressed by said memory address logic means, said storing means including:(a5a) said internal PROM memory; (a5b) an external RAM memory means; (a5c) an external register means; (b) multiple bus means connecting said I/O processing means and said application dependent logic module, said bus means including:(b1) an I/O bus connected to said internal arithmetic logic circuitry for transmitting data to and receiving data from said application dependent logic module; (b2) a memory address bus from said memory address logic means for carrying addresses to said external RAM memory means; (b3) an external memory output data bus for carrying data from said external RAM memory means to said I/O processing means; (b4) an external register bus connecting said external register means to said external RAM memory means; (b5) a host transfer bus connecting said external register means to said host computer; (b6) a peripheral transfer bus connecting said external register means to a peripheral terminal unit: (c) said application dependent logic module connected to said I/O processing means via said multiple bus means, said logic module including:(c1) said external RAM memory means for storage of data-in-transit and for storage of data to be processed by said I/O processing means, and for storage of data-in-transit before and after processing by said I/O processing means; (c2) control logic means, responsive to instructions from said I/O processing means, for controlling data transferred into and out of said external RAM memory means and said external register means, said control logic means including:(c2-1) address decoder means, responsive to special addresses of said RAM memory means and said external register means, said address decoder means including:(c2-1a) means to generate a WAIT signal, upon recognition of said special address, said WAIT signal initiating said delay-clock circuit means; said means to generate including: (c2-1a-1) hardwired circuit means responsive to preset addresses received from said I/O processing means, and for generating said WAIT signal to said delay-clock circuit means; (c2-1b) connection means to transmit said WAIT signal to said decoder-controller in said I/O processing means; (c3) external register means connected to said I/O bus, to said external RAM memory means, and to said host computer, said external register means functioning to receive or transmit data under control of said delay-clock circuit means from said instruction decoder-controller.
 4. In a system having a basic clock signal whereby an I/O processing means controls an application dependent logic module which is used to transfer data between a main host computer and a peripheral terminal, and wherein said I/O processing means retrieves data from said application dependent logic module in order to edit and process said data for return back to said application dependent logic module and wherein said I/O processing means operates at a much higher data transfer rate than is provided by connected slow device means, such as external registers and memories in said application dependent logic module, a system for reducing the rate of data transfer between said I/O processing means and said application dependent logic module, said system comprising:(a) I/O processing means for executing data transfers between said main host computer and said application dependent logic module and for executing data transfers between a peripheral terminal and said application dependent logic module, said processing means retrieving data-in-transit within said application dependent logic module for editing and processing and for return to said application dependent logic module, said I/O processing means including:(a1) delay-clock circuit means having a first input from said basic clock signal and a second input from a wait-delay signal derived from a sensing means in said application dependent logic module, said delay-clock circuit means operating to alter the basic clock signal to a rate acceptable to said slow device means; (b) an application dependent logic module, controlled by said I/O processing means, for temporary storage of data-in-transit and wherein said application dependent logic module includes devices which have a slower rate of acceptability of data transfers than the output transfer rate of said I/O processing means and wherein said application dependent logic module includes:(b1) external RAM memory slow device means for storage of data-in-transit and for storage of data before and after processing by said I/O processing means; (b2) external register slow device means, connected to said external RAM memory means, to said main host computer, and to said I/O processing means for temporary storage of data-in-transit between said main host computer and said peripheral terminal; (b3) means for sensing addresses of said slow device means and generating said wait-delay signal to said I/O processing means to cause said I/O processing means to slow down the data transfer rate of said I/O processing means to a rate acceptable to said slow device means.
 5. In a data transfer network wherein a main host computer initiates instructions to/from a plurality of peripheral terminals via a peripheral-controller mounted in a base module wherein said base module includes a distribution control card circuit, to connect and/or disconnect said host computer to said peripheral-controller, and said base module includes a maintenance card circuit for providing basic clock signals and test signals to said peripheral-conroller, said peripheral-controller comprising:(a) a universal processor means functioning, after initiation by instruction from said main host computer, to generate and execute data transfer commands to data transfer operations between said host computer and selected peripheral terminals via an application dependent logic module, said universal processor means including:(a1) processor clock circuitry having output clock signals for strobing an I/O bus which transfers data from said universal processor means at an altered basic clock rate of said processor means, said clock circuitry including:(i) first input means for receiving basic clock signals from said maintenance card circuit; (ii) second input means for receiving a WAIT signal from said application dependent logic module; and wherein said processor clock circuitry provides output clock signals for strobing said I/O bus at the basic clock rate when said WAIT signal is inactive, and for disabling the strobing of said I/O bus when said WAIT signal to active to generate said altered basic clock rate; (b) said application-dependent logic module inter-cooperating with said processor means and functioning to control data transfers to/from selected peripheral terminals, said logic module including:(b1) a slow memory for holding data-transfer programs for peripheral terminals and for temporarily storing data undergoing transfer, said slow memory also functioning to store data destined for a slow peripheral terminal, said data stored therein being transferred to said peripheral terminal via an external slow register at a slower rate by the temporary disabling of the strobing of said I/O bus by said processor clock circuitry, said slow memory connected to receive address data from said universal processor means and to transfer accessed data to said universal processor means; (b2) said external slow register means for temporarily holding instructions and data undergoing transfer, said slow register means having bus connections to said main host system and to said plurality of peripheral terminals, said slow register means connected to receive data from said I/O bus at said altered clock rate determined by said processor clock circuitry; (b3) control logic means for signaling said slow memory, said slow register means, and said universal processor means, and including:(b3-1) address decoder means for sensing address signals from said universal processor means and directed to said slow memory or to said slow register, said address decoder means including means to generate a WAIT signal to temporarily disable said processor clock circuitry for a set number of clock cycles to establish a slower rate of data transfer than the basic clock rate of said processor system, said slower rate occurring due to the temporary disabling of said processor clock circuitry which slows the clocking of said universal processor means and the strobing of said I/O bus; (c) bus means including:(c1) an I/O bus for carrying instructions and data from said universal processor means to said slow memory, to said slow register, and to said control logic means; (c2) a memory address bus for carrying addresses from said universal processor means to said slow memory and to said address decoder means; (c3) a memory data output bus for carrying instructions and data from said slow memory to said universal processor means; (c4) control lines for communication and control between said application dependent logic module and said universal processor means. 